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 $186.86   7.665%   $201.1828   $201.18   $201.20   $201.20  
  Purchase #2 $179.96   13.479%   $204.2168   $204.22   $204.20   $204.20  
  Purchase #3 $139.95   11.223%   $155.6566   $155.66   $155.65   $155.70  
  Purchase #4 $62.91   8.802%   $68.4473   $68.45   $68.45   $68.40  
  Purchase #5 $225.82   13.127%   $255.4634   $255.46   $255.45   $255.50  
  Purchase #6 $87.97   7.352%   $94.4376   $94.44   $94.45   $94.40  
  Purchase #7 $42.72   8.288%   $46.2606   $46.26   $46.25   $46.30  
  7 purchase totals = $926.19       $1,025.6651   $1,025.67   $1,025.65   $1,025.70