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 $194.86   7.591%   $209.6518   $209.65   $209.65   $209.70  
  Purchase #2 $215.90   7.398%   $231.8723   $231.87   $231.85   $231.90  
  Purchase #3 $19.28   11.449%   $21.4874   $21.49   $21.50   $21.50  
  Purchase #4 $233.59   5.277%   $245.9165   $245.92   $245.90   $245.90  
  Purchase #5 $94.91   13.733%   $107.944   $107.94   $107.95   $107.90  
  Purchase #6 $165.95   5.792%   $175.5618   $175.56   $175.55   $175.60  
  Purchase #7 $94.87   12.662%   $106.8824   $106.88   $106.90   $106.90  
  7 purchase totals = $1,019.36       $1,099.3162   $1,099.31   $1,099.30   $1,099.40