Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $174.97   11.467%   $195.0338   $195.03   $195.05   $195.00  
  Purchase #2 $244.52   9.479%   $267.6981   $267.70   $267.70   $267.70  
  Purchase #3 $186.49   13.193%   $211.0936   $211.09   $211.10   $211.10  
  Purchase #4 $197.46   5.325%   $207.9747   $207.97   $207.95   $208.00  
  Purchase #5 $131.51   12.219%   $147.5792   $147.58   $147.60   $147.60  
  Purchase #6 $203.62   9.385%   $222.7297   $222.73   $222.75   $222.70  
  Purchase #7 $134.26   4.202%   $139.9016   $139.90   $139.90   $139.90  
  7 purchase totals = $1,272.83       $1,392.0107   $1,392.00   $1,392.05   $1,392.00