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 $91.67   3.676%   $95.0398   $95.04   $95.05   $95.00  
  Purchase #2 $189.74   6.268%   $201.6329   $201.63   $201.65   $201.60  
  Purchase #3 $202.74   13.127%   $229.3537   $229.35   $229.35   $229.40  
  Purchase #4 $149.60   5.480%   $157.7981   $157.80   $157.80   $157.80  
  Purchase #5 $91.80   6.114%   $97.4127   $97.41   $97.40   $97.40  
  Purchase #6 $236.63   7.541%   $254.4743   $254.47   $254.45   $254.50  
  Purchase #7 $70.98   4.170%   $73.9399   $73.94   $73.95   $73.90  
  7 purchase totals = $1,033.16       $1,109.6514   $1,109.64   $1,109.65   $1,109.60