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 $141.52   7.629%   $152.3166   $152.32   $152.30   $152.30  
  Purchase #2 $197.41   4.473%   $206.2401   $206.24   $206.25   $206.20  
  Purchase #3 $159.65   8.365%   $173.0047   $173.00   $173.00   $173.00  
  Purchase #4 $66.35   13.645%   $75.4035   $75.40   $75.40   $75.40  
  Purchase #5 $42.93   8.567%   $46.6078   $46.61   $46.60   $46.60  
  Purchase #6 $50.87   13.497%   $57.7359   $57.74   $57.75   $57.70  
  Purchase #7 $44.94   8.331%   $48.684   $48.68   $48.70   $48.70  
  7 purchase totals = $703.67       $759.9926   $759.99   $760.00   $759.90