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 $195.42   6.111%   $207.3621   $207.36   $207.35   $207.40  
  Purchase #2 $40.92   4.479%   $42.7528   $42.75   $42.75   $42.80  
  Purchase #3 $59.97   3.395%   $62.006   $62.01   $62.00   $62.00  
  Purchase #4 $41.67   4.371%   $43.4914   $43.49   $43.50   $43.50  
  Purchase #5 $197.49   10.295%   $217.8216   $217.82   $217.80   $217.80  
  Purchase #6 $68.70   5.252%   $72.3081   $72.31   $72.30   $72.30  
  Purchase #7 $85.48   11.343%   $95.176   $95.18   $95.20   $95.20  
  7 purchase totals = $689.65       $740.9180   $740.92   $740.90   $741.00