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 $184.48   10.163%   $203.2287   $203.23   $203.25   $203.20  
  Purchase #2 $204.71   8.570%   $222.2536   $222.25   $222.25   $222.30  
  Purchase #3 $68.32   9.747%   $74.9792   $74.98   $75.00   $75.00  
  Purchase #4 $113.99   4.684%   $119.3293   $119.33   $119.35   $119.30  
  Purchase #5 $122.96   11.633%   $137.2639   $137.26   $137.25   $137.30  
  Purchase #6 $225.53   8.197%   $244.0167   $244.02   $244.00   $244.00  
  Purchase #7 $55.27   7.755%   $59.5562   $59.56   $59.55   $59.60  
  7 purchase totals = $975.26       $1,060.6276   $1,060.63   $1,060.65   $1,060.70