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 $44.58   3.288%   $46.0458   $46.05   $46.05   $46.00  
  Purchase #2 $141.59   12.563%   $159.378   $159.38   $159.40   $159.40  
  Purchase #3 $235.33   3.654%   $243.929   $243.93   $243.95   $243.90  
  Purchase #4 $58.36   5.543%   $61.5949   $61.59   $61.60   $61.60  
  Purchase #5 $54.87   7.331%   $58.8925   $58.89   $58.90   $58.90  
  Purchase #6 $55.94   3.148%   $57.701   $57.70   $57.70   $57.70  
  Purchase #7 $170.98   9.736%   $187.6266   $187.63   $187.65   $187.60  
  7 purchase totals = $761.65       $815.1678   $815.17   $815.25   $815.10