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 $112.96   4.206%   $117.7111   $117.71   $117.70   $117.70  
  Purchase #2 $211.69   12.524%   $238.2021   $238.20   $238.20   $238.20  
  Purchase #3 $24.57   9.213%   $26.8336   $26.83   $26.85   $26.80  
  Purchase #4 $80.79   7.375%   $86.7483   $86.75   $86.75   $86.70  
  Purchase #5 $88.45   3.117%   $91.207   $91.21   $91.20   $91.20  
  Purchase #6 $98.64   5.567%   $104.1313   $104.13   $104.15   $104.10  
  Purchase #7 $55.49   11.646%   $61.9524   $61.95   $61.95   $62.00  
  7 purchase totals = $672.59       $726.7858   $726.78   $726.80   $726.70