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 $177.76   9.846%   $195.2622   $195.26   $195.25   $195.30  
  Purchase #2 $206.96   13.688%   $235.2887   $235.29   $235.30   $235.30  
  Purchase #3 $153.86   11.442%   $171.4647   $171.46   $171.45   $171.50  
  Purchase #4 $151.59   6.807%   $161.9087   $161.91   $161.90   $161.90  
  Purchase #5 $167.32   7.794%   $180.3609   $180.36   $180.35   $180.40  
  Purchase #6 $213.95   9.646%   $234.5876   $234.59   $234.60   $234.60  
  Purchase #7 $244.94   5.732%   $258.98   $258.98   $259.00   $259.00  
  7 purchase totals = $1,316.38       $1,437.8528   $1,437.85   $1,437.85   $1,438.00