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 $119.43   5.456%   $125.9461   $125.95   $125.95   $125.90  
  Purchase #2 $107.86   11.446%   $120.2057   $120.21   $120.20   $120.20  
  Purchase #3 $93.99   12.438%   $105.6805   $105.68   $105.70   $105.70  
  Purchase #4 $20.90   4.849%   $21.9134   $21.91   $21.90   $21.90  
  Purchase #5 $201.63   10.261%   $222.3193   $222.32   $222.30   $222.30  
  Purchase #6 $241.33   5.842%   $255.4285   $255.43   $255.45   $255.40  
  Purchase #7 $182.34   10.301%   $201.1228   $201.12   $201.10   $201.10  
  7 purchase totals = $967.48       $1,052.6163   $1,052.62   $1,052.60   $1,052.50