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 $41.73   10.304%   $46.0299   $46.03   $46.05   $46.00  
  Purchase #2 $51.29   10.530%   $56.6908   $56.69   $56.70   $56.70  
  Purchase #3 $230.39   5.808%   $243.7711   $243.77   $243.75   $243.80  
  Purchase #4 $141.83   5.237%   $149.2576   $149.26   $149.25   $149.30  
  Purchase #5 $158.50   9.150%   $173.0028   $173.00   $173.00   $173.00  
  Purchase #6 $209.54   4.693%   $219.3737   $219.37   $219.35   $219.40  
  Purchase #7 $64.96   13.589%   $73.7874   $73.79   $73.80   $73.80  
  7 purchase totals = $898.24       $961.9133   $961.91   $961.90   $962.00