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 $206.35   9.561%   $226.0791   $226.08   $226.10   $226.10  
  Purchase #2 $194.60   4.729%   $203.8026   $203.80   $203.80   $203.80  
  Purchase #3 $28.36   13.570%   $32.2085   $32.21   $32.20   $32.20  
  Purchase #4 $185.34   6.521%   $197.426   $197.43   $197.45   $197.40  
  Purchase #5 $119.97   4.572%   $125.455   $125.46   $125.45   $125.50  
  Purchase #6 $236.65   13.406%   $268.3753   $268.38   $268.40   $268.40  
  Purchase #7 $104.36   10.767%   $115.5964   $115.60   $115.60   $115.60  
  7 purchase totals = $1,075.63       $1,168.9429   $1,168.96   $1,169.00   $1,169.00