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 $194.60   3.797%   $201.989   $201.99   $202.00   $202.00  
  Purchase #2 $203.96   5.108%   $214.3783   $214.38   $214.40   $214.40  
  Purchase #3 $93.84   12.707%   $105.7642   $105.76   $105.75   $105.80  
  Purchase #4 $58.73   13.136%   $66.4448   $66.44   $66.45   $66.40  
  Purchase #5 $227.35   8.178%   $245.9427   $245.94   $245.95   $245.90  
  Purchase #6 $226.25   3.183%   $233.4515   $233.45   $233.45   $233.50  
  Purchase #7 $23.60   8.500%   $25.606   $25.61   $25.60   $25.60  
  7 purchase totals = $1,028.33       $1,093.5765   $1,093.57   $1,093.60   $1,093.60