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 $85.81   7.779%   $92.4852   $92.49   $92.50   $92.50  
  Purchase #2 $66.61   6.510%   $70.9463   $70.95   $70.95   $70.90  
  Purchase #3 $230.41   6.282%   $244.8844   $244.88   $244.90   $244.90  
  Purchase #4 $107.31   10.624%   $118.7106   $118.71   $118.70   $118.70  
  Purchase #5 $141.60   7.656%   $152.4409   $152.44   $152.45   $152.40  
  Purchase #6 $239.66   10.582%   $265.0208   $265.02   $265.00   $265.00  
  Purchase #7 $240.53   4.530%   $251.426   $251.43   $251.45   $251.40  
  7 purchase totals = $1,111.93       $1,195.9142   $1,195.92   $1,195.95   $1,195.80