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 $114.90   3.284%   $118.6733   $118.67   $118.65   $118.70  
  Purchase #2 $189.72   11.798%   $212.1032   $212.10   $212.10   $212.10  
  Purchase #3 $200.80   9.650%   $220.1772   $220.18   $220.20   $220.20  
  Purchase #4 $99.51   9.442%   $108.9057   $108.91   $108.90   $108.90  
  Purchase #5 $229.73   5.624%   $242.65   $242.65   $242.65   $242.70  
  Purchase #6 $94.75   11.243%   $105.4027   $105.40   $105.40   $105.40  
  Purchase #7 $133.97   7.200%   $143.6158   $143.62   $143.60   $143.60  
  7 purchase totals = $1,063.38       $1,151.5279   $1,151.53   $1,151.50   $1,151.60