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 $157.41   11.843%   $176.0521   $176.05   $176.05   $176.10  
  Purchase #2 $193.52   3.313%   $199.9313   $199.93   $199.95   $199.90  
  Purchase #3 $31.45   7.201%   $33.7147   $33.71   $33.70   $33.70  
  Purchase #4 $243.86   5.779%   $257.9527   $257.95   $257.95   $258.00  
  Purchase #5 $184.78   9.268%   $201.9054   $201.91   $201.90   $201.90  
  Purchase #6 $26.35   13.645%   $29.9455   $29.95   $29.95   $29.90  
  Purchase #7 $176.36   10.855%   $195.5039   $195.50   $195.50   $195.50  
  7 purchase totals = $1,013.73       $1,095.0056   $1,095.00   $1,095.00   $1,095.00