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 $244.80   6.529%   $260.783   $260.78   $260.80   $260.80  
  Purchase #2 $60.92   6.813%   $65.0705   $65.07   $65.05   $65.10  
  Purchase #3 $169.67   10.817%   $188.0232   $188.02   $188.00   $188.00  
  Purchase #4 $169.27   8.826%   $184.2098   $184.21   $184.20   $184.20  
  Purchase #5 $55.53   5.222%   $58.4298   $58.43   $58.45   $58.40  
  Purchase #6 $196.91   10.262%   $217.1169   $217.12   $217.10   $217.10  
  Purchase #7 $40.80   7.591%   $43.8971   $43.90   $43.90   $43.90  
  7 purchase totals = $937.90       $1,017.5303   $1,017.53   $1,017.50   $1,017.50