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 $122.34   8.163%   $132.3266   $132.33   $132.35   $132.30  
  Purchase #2 $246.91   8.237%   $267.248   $267.25   $267.25   $267.20  
  Purchase #3 $190.41   5.541%   $200.9606   $200.96   $200.95   $201.00  
  Purchase #4 $114.77   4.852%   $120.3386   $120.34   $120.35   $120.30  
  Purchase #5 $59.73   7.807%   $64.3931   $64.39   $64.40   $64.40  
  Purchase #6 $76.90   12.342%   $86.391   $86.39   $86.40   $86.40  
  Purchase #7 $73.59   9.281%   $80.4199   $80.42   $80.40   $80.40  
  7 purchase totals = $884.65       $952.0778   $952.08   $952.10   $952.00