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 $182.99   8.772%   $199.0419   $199.04   $199.05   $199.00  
  Purchase #2 $184.96   11.819%   $206.8204   $206.82   $206.80   $206.80  
  Purchase #3 $205.95   9.579%   $225.678   $225.68   $225.70   $225.70  
  Purchase #4 $92.94   4.823%   $97.4225   $97.42   $97.40   $97.40  
  Purchase #5 $82.87   7.370%   $88.9775   $88.98   $89.00   $89.00  
  Purchase #6 $183.58   6.208%   $194.9766   $194.98   $195.00   $195.00  
  Purchase #7 $130.67   8.149%   $141.3183   $141.32   $141.30   $141.30  
  7 purchase totals = $1,063.96       $1,154.2352   $1,154.24   $1,154.25   $1,154.20