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 $187.49   8.234%   $202.9279   $202.93   $202.95   $202.90  
  Purchase #2 $23.39   7.356%   $25.1106   $25.11   $25.10   $25.10  
  Purchase #3 $19.59   5.137%   $20.5963   $20.60   $20.60   $20.60  
  Purchase #4 $119.38   6.745%   $127.4322   $127.43   $127.45   $127.40  
  Purchase #5 $71.61   3.241%   $73.9309   $73.93   $73.95   $73.90  
  Purchase #6 $176.47   13.769%   $200.7682   $200.77   $200.75   $200.80  
  Purchase #7 $84.41   3.331%   $87.2217   $87.22   $87.20   $87.20  
  7 purchase totals = $682.34       $737.9878   $737.99   $738.00   $737.90