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 $90.79   5.242%   $95.5492   $95.55   $95.55   $95.50  
  Purchase #2 $236.30   12.434%   $265.6815   $265.68   $265.70   $265.70  
  Purchase #3 $81.96   6.492%   $87.2808   $87.28   $87.30   $87.30  
  Purchase #4 $82.67   6.146%   $87.7509   $87.75   $87.75   $87.80  
  Purchase #5 $103.58   5.634%   $109.4157   $109.42   $109.40   $109.40  
  Purchase #6 $98.73   8.502%   $107.124   $107.12   $107.10   $107.10  
  Purchase #7 $187.46   12.202%   $210.3339   $210.33   $210.35   $210.30  
  7 purchase totals = $881.49       $963.1360   $963.13   $963.15   $963.10