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 $82.96   13.260%   $93.9605   $93.96   $93.95   $94.00  
  Purchase #2 $197.29   5.219%   $207.5866   $207.59   $207.60   $207.60  
  Purchase #3 $200.41   6.362%   $213.1601   $213.16   $213.15   $213.20  
  Purchase #4 $237.99   6.567%   $253.6188   $253.62   $253.60   $253.60  
  Purchase #5 $197.93   6.256%   $210.3125   $210.31   $210.30   $210.30  
  Purchase #6 $131.78   10.475%   $145.584   $145.58   $145.60   $145.60  
  Purchase #7 $220.39   8.834%   $239.8593   $239.86   $239.85   $239.90  
  7 purchase totals = $1,268.75       $1,364.0818   $1,364.08   $1,364.05   $1,364.20