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 $61.51   10.859%   $68.1894   $68.19   $68.20   $68.20  
  Purchase #2 $41.33   11.559%   $46.1073   $46.11   $46.10   $46.10  
  Purchase #3 $169.86   10.807%   $188.2168   $188.22   $188.20   $188.20  
  Purchase #4 $78.54   7.608%   $84.5153   $84.52   $84.50   $84.50  
  Purchase #5 $85.82   10.647%   $94.9573   $94.96   $94.95   $95.00  
  Purchase #6 $215.95   4.788%   $226.2897   $226.29   $226.30   $226.30  
  Purchase #7 $234.85   10.227%   $258.8681   $258.87   $258.85   $258.90  
  7 purchase totals = $887.86       $967.1439   $967.16   $967.10   $967.20