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 $173.65   12.266%   $194.9499   $194.95   $194.95   $194.90  
  Purchase #2 $180.64   12.634%   $203.4621   $203.46   $203.45   $203.50  
  Purchase #3 $210.53   11.131%   $233.9641   $233.96   $233.95   $234.00  
  Purchase #4 $99.43   5.609%   $105.007   $105.01   $105.00   $105.00  
  Purchase #5 $105.70   12.748%   $119.1746   $119.17   $119.15   $119.20  
  Purchase #6 $48.46   7.582%   $52.1342   $52.13   $52.15   $52.10  
  Purchase #7 $14.83   7.766%   $15.9817   $15.98   $16.00   $16.00  
  7 purchase totals = $833.24       $924.6736   $924.66   $924.65   $924.70