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 $214.47   8.731%   $233.1954   $233.20   $233.20   $233.20  
  Purchase #2 $195.78   9.331%   $214.0482   $214.05   $214.05   $214.00  
  Purchase #3 $112.28   6.655%   $119.7522   $119.75   $119.75   $119.80  
  Purchase #4 $52.96   10.472%   $58.506   $58.51   $58.50   $58.50  
  Purchase #5 $239.50   7.326%   $257.0458   $257.05   $257.05   $257.00  
  Purchase #6 $217.41   7.434%   $233.5723   $233.57   $233.55   $233.60  
  Purchase #7 $219.73   11.196%   $244.331   $244.33   $244.35   $244.30  
  7 purchase totals = $1,252.13       $1,360.4509   $1,360.46   $1,360.45   $1,360.40