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 $88.49   7.478%   $95.1073   $95.11   $95.10   $95.10  
  Purchase #2 $21.69   5.517%   $22.8866   $22.89   $22.90   $22.90  
  Purchase #3 $64.66   6.661%   $68.967   $68.97   $68.95   $69.00  
  Purchase #4 $118.93   3.378%   $122.9475   $122.95   $122.95   $122.90  
  Purchase #5 $196.75   6.762%   $210.0542   $210.05   $210.05   $210.10  
  Purchase #6 $127.43   9.191%   $139.1421   $139.14   $139.15   $139.10  
  Purchase #7 $185.31   11.415%   $206.4631   $206.46   $206.45   $206.50  
  7 purchase totals = $803.26       $865.5678   $865.57   $865.55   $865.60