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 $188.28   4.538%   $196.8241   $196.82   $196.80   $196.80  
  Purchase #2 $143.96   13.153%   $162.8951   $162.90   $162.90   $162.90  
  Purchase #3 $95.66   11.720%   $106.8714   $106.87   $106.85   $106.90  
  Purchase #4 $9.84   3.507%   $10.1851   $10.19   $10.20   $10.20  
  Purchase #5 $189.79   10.353%   $209.439   $209.44   $209.45   $209.40  
  Purchase #6 $234.62   4.680%   $245.6002   $245.60   $245.60   $245.60  
  Purchase #7 $97.92   3.573%   $101.4187   $101.42   $101.40   $101.40  
  7 purchase totals = $960.07       $1,033.2336   $1,033.24   $1,033.20   $1,033.20