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 $192.33   5.155%   $202.2446   $202.24   $202.25   $202.20  
  Purchase #2 $160.68   5.302%   $169.1993   $169.20   $169.20   $169.20  
  Purchase #3 $237.34   7.534%   $255.2212   $255.22   $255.20   $255.20  
  Purchase #4 $46.71   12.524%   $52.56   $52.56   $52.55   $52.60  
  Purchase #5 $114.78   10.224%   $126.5151   $126.52   $126.50   $126.50  
  Purchase #6 $32.76   9.587%   $35.9007   $35.90   $35.90   $35.90  
  Purchase #7 $164.76   9.830%   $180.9559   $180.96   $180.95   $181.00  
  7 purchase totals = $949.36       $1,022.5968   $1,022.60   $1,022.55   $1,022.60