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 $117.96   6.308%   $125.4009   $125.40   $125.40   $125.40  
  Purchase #2 $178.71   11.185%   $198.6987   $198.70   $198.70   $198.70  
  Purchase #3 $57.84   6.762%   $61.7511   $61.75   $61.75   $61.80  
  Purchase #4 $176.82   4.534%   $184.837   $184.84   $184.85   $184.80  
  Purchase #5 $88.41   6.348%   $94.0223   $94.02   $94.00   $94.00  
  Purchase #6 $152.50   11.746%   $170.4127   $170.41   $170.40   $170.40  
  Purchase #7 $199.91   3.107%   $206.1212   $206.12   $206.10   $206.10  
  7 purchase totals = $972.15       $1,041.2439   $1,041.24   $1,041.20   $1,041.20