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 $176.94   12.159%   $198.4541   $198.45   $198.45   $198.50  
  Purchase #2 $92.52   3.148%   $95.4325   $95.43   $95.45   $95.40  
  Purchase #3 $212.41   5.462%   $224.0118   $224.01   $224.00   $224.00  
  Purchase #4 $218.46   11.862%   $244.3737   $244.37   $244.35   $244.40  
  Purchase #5 $210.63   5.108%   $221.389   $221.39   $221.40   $221.40  
  Purchase #6 $135.42   11.710%   $151.2777   $151.28   $151.30   $151.30  
  Purchase #7 $205.64   13.211%   $232.8071   $232.81   $232.80   $232.80  
  7 purchase totals = $1,252.02       $1,367.7459   $1,367.74   $1,367.75   $1,367.80