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 $13.46   7.825%   $14.5132   $14.51   $14.50   $14.50  
  Purchase #2 $96.74   13.340%   $109.6451   $109.65   $109.65   $109.60  
  Purchase #3 $182.87   12.624%   $205.9555   $205.96   $205.95   $206.00  
  Purchase #4 $210.73   10.860%   $233.6153   $233.62   $233.60   $233.60  
  Purchase #5 $128.97   13.494%   $146.3732   $146.37   $146.35   $146.40  
  Purchase #6 $219.67   8.788%   $238.9746   $238.97   $238.95   $239.00  
  Purchase #7 $95.52   9.584%   $104.6746   $104.67   $104.65   $104.70  
  7 purchase totals = $947.96       $1,053.7515   $1,053.75   $1,053.65   $1,053.80