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 $24.72   4.844%   $25.9174   $25.92   $25.90   $25.90  
  Purchase #2 $71.74   4.545%   $75.0006   $75.00   $75.00   $75.00  
  Purchase #3 $169.88   10.382%   $187.5169   $187.52   $187.50   $187.50  
  Purchase #4 $11.90   13.675%   $13.5273   $13.53   $13.55   $13.50  
  Purchase #5 $176.78   6.512%   $188.2919   $188.29   $188.30   $188.30  
  Purchase #6 $222.81   10.833%   $246.947   $246.95   $246.95   $246.90  
  Purchase #7 $23.92   5.422%   $25.2169   $25.22   $25.20   $25.20  
  7 purchase totals = $701.75       $762.4180   $762.43   $762.40   $762.30