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 $151.76   7.371%   $162.9462   $162.95   $162.95   $162.90  
  Purchase #2 $45.37   3.305%   $46.8695   $46.87   $46.85   $46.90  
  Purchase #3 $61.33   4.571%   $64.1334   $64.13   $64.15   $64.10  
  Purchase #4 $88.29   11.745%   $98.6597   $98.66   $98.65   $98.70  
  Purchase #5 $242.59   12.168%   $272.1084   $272.11   $272.10   $272.10  
  Purchase #6 $156.36   12.846%   $176.446   $176.45   $176.45   $176.40  
  Purchase #7 $95.72   7.352%   $102.7573   $102.76   $102.75   $102.80  
  7 purchase totals = $841.42       $923.9205   $923.93   $923.90   $923.90