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 $167.46   4.290%   $174.644   $174.64   $174.65   $174.60  
  Purchase #2 $154.63   7.412%   $166.0912   $166.09   $166.10   $166.10  
  Purchase #3 $171.46   3.234%   $177.005   $177.01   $177.00   $177.00  
  Purchase #4 $68.57   6.482%   $73.0147   $73.01   $73.00   $73.00  
  Purchase #5 $194.89   6.216%   $207.0044   $207.00   $207.00   $207.00  
  Purchase #6 $167.89   13.248%   $190.1321   $190.13   $190.15   $190.10  
  Purchase #7 $181.72   11.834%   $203.2247   $203.22   $203.20   $203.20  
  7 purchase totals = $1,106.62       $1,191.1161   $1,191.10   $1,191.10   $1,191.00