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 $62.47   11.778%   $69.8277   $69.83   $69.85   $69.80  
  Purchase #2 $140.50   6.342%   $149.4105   $149.41   $149.40   $149.40  
  Purchase #3 $12.84   10.723%   $14.2168   $14.22   $14.20   $14.20  
  Purchase #4 $194.41   3.221%   $200.6719   $200.67   $200.65   $200.70  
  Purchase #5 $74.54   11.661%   $83.2321   $83.23   $83.25   $83.20  
  Purchase #6 $59.70   8.323%   $64.6688   $64.67   $64.65   $64.70  
  Purchase #7 $147.49   5.303%   $155.3114   $155.31   $155.30   $155.30  
  7 purchase totals = $691.95       $737.3392   $737.34   $737.30   $737.30