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 $114.72   9.590%   $125.7216   $125.72   $125.70   $125.70  
  Purchase #2 $244.97   4.157%   $255.1534   $255.15   $255.15   $255.20  
  Purchase #3 $82.50   13.218%   $93.4049   $93.40   $93.40   $93.40  
  Purchase #4 $42.51   9.752%   $46.6556   $46.66   $46.65   $46.70  
  Purchase #5 $147.61   5.557%   $155.8127   $155.81   $155.80   $155.80  
  Purchase #6 $207.96   4.809%   $217.9608   $217.96   $217.95   $218.00  
  Purchase #7 $138.86   9.707%   $152.3391   $152.34   $152.35   $152.30  
  7 purchase totals = $979.13       $1,047.0481   $1,047.04   $1,047.00   $1,047.10