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 $114.45   3.361%   $118.2967   $118.30   $118.30   $118.30  
  Purchase #2 $39.56   3.313%   $40.8706   $40.87   $40.85   $40.90  
  Purchase #3 $149.83   7.491%   $161.0538   $161.05   $161.05   $161.10  
  Purchase #4 $157.58   12.209%   $176.8189   $176.82   $176.80   $176.80  
  Purchase #5 $234.53   5.418%   $247.2368   $247.24   $247.25   $247.20  
  Purchase #6 $32.30   11.370%   $35.9725   $35.97   $35.95   $36.00  
  Purchase #7 $238.70   11.841%   $266.9645   $266.96   $266.95   $267.00  
  7 purchase totals = $966.95       $1,047.2138   $1,047.21   $1,047.15   $1,047.30