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 $209.36   13.470%   $237.5608   $237.56   $237.55   $237.60  
  Purchase #2 $177.41   9.697%   $194.6134   $194.61   $194.60   $194.60  
  Purchase #3 $140.44   6.608%   $149.7203   $149.72   $149.70   $149.70  
  Purchase #4 $231.84   5.501%   $244.5935   $244.59   $244.60   $244.60  
  Purchase #5 $197.49   9.587%   $216.4234   $216.42   $216.40   $216.40  
  Purchase #6 $95.99   9.684%   $105.2857   $105.29   $105.30   $105.30  
  Purchase #7 $48.49   10.873%   $53.7623   $53.76   $53.75   $53.80  
  7 purchase totals = $1,101.02       $1,201.9594   $1,201.95   $1,201.90   $1,202.00