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 $212.99   10.639%   $235.65   $235.65   $235.65   $235.70  
  Purchase #2 $73.43   3.503%   $76.0023   $76.00   $76.00   $76.00  
  Purchase #3 $99.97   3.286%   $103.255   $103.26   $103.25   $103.30  
  Purchase #4 $28.79   6.800%   $30.7477   $30.75   $30.75   $30.70  
  Purchase #5 $240.73   11.481%   $268.3682   $268.37   $268.35   $268.40  
  Purchase #6 $217.71   12.359%   $244.6168   $244.62   $244.60   $244.60  
  Purchase #7 $84.52   12.182%   $94.8162   $94.82   $94.80   $94.80  
  7 purchase totals = $958.14       $1,053.4562   $1,053.47   $1,053.40   $1,053.50