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 $85.58   10.331%   $94.4213   $94.42   $94.40   $94.40  
  Purchase #2 $150.53   11.443%   $167.7551   $167.76   $167.75   $167.80  
  Purchase #3 $231.38   6.786%   $247.0814   $247.08   $247.10   $247.10  
  Purchase #4 $189.97   10.412%   $209.7497   $209.75   $209.75   $209.70  
  Purchase #5 $193.85   11.263%   $215.6833   $215.68   $215.70   $215.70  
  Purchase #6 $54.89   12.862%   $61.95   $61.95   $61.95   $62.00  
  Purchase #7 $188.51   6.347%   $200.4747   $200.47   $200.45   $200.50  
  7 purchase totals = $1,094.71       $1,197.1155   $1,197.11   $1,197.10   $1,197.20