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 $83.79   10.615%   $92.6843   $92.68   $92.70   $92.70  
  Purchase #2 $245.49   6.523%   $261.5033   $261.50   $261.50   $261.50  
  Purchase #3 $92.49   4.532%   $96.6816   $96.68   $96.70   $96.70  
  Purchase #4 $142.82   10.847%   $158.3117   $158.31   $158.30   $158.30  
  Purchase #5 $204.51   5.732%   $216.2325   $216.23   $216.25   $216.20  
  Purchase #6 $160.98   8.344%   $174.4122   $174.41   $174.40   $174.40  
  Purchase #7 $109.52   3.845%   $113.731   $113.73   $113.75   $113.70  
  7 purchase totals = $1,039.60       $1,113.5566   $1,113.54   $1,113.60   $1,113.50