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 $174.53   11.837%   $195.1891   $195.19   $195.20   $195.20  
  Purchase #2 $154.34   9.267%   $168.6427   $168.64   $168.65   $168.60  
  Purchase #3 $23.53   4.230%   $24.5253   $24.53   $24.55   $24.50  
  Purchase #4 $156.43   5.626%   $165.2308   $165.23   $165.25   $165.20  
  Purchase #5 $91.84   12.763%   $103.5615   $103.56   $103.55   $103.60  
  Purchase #6 $226.81   12.690%   $255.5922   $255.59   $255.60   $255.60  
  Purchase #7 $106.65   13.104%   $120.6254   $120.63   $120.65   $120.60  
  7 purchase totals = $934.13       $1,033.3670   $1,033.37   $1,033.45   $1,033.30