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 $47.81   9.330%   $52.2707   $52.27   $52.25   $52.30  
  Purchase #2 $117.35   9.376%   $128.3527   $128.35   $128.35   $128.40  
  Purchase #3 $65.35   7.398%   $70.1846   $70.18   $70.20   $70.20  
  Purchase #4 $98.64   9.629%   $108.138   $108.14   $108.15   $108.10  
  Purchase #5 $125.91   4.817%   $131.9751   $131.98   $132.00   $132.00  
  Purchase #6 $212.53   7.663%   $228.8162   $228.82   $228.80   $228.80  
  Purchase #7 $66.92   10.856%   $74.1848   $74.18   $74.20   $74.20  
  7 purchase totals = $734.51       $793.9221   $793.92   $793.95   $794.00