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 $174.32   5.701%   $184.258   $184.26   $184.25   $184.30  
  Purchase #2 $192.88   7.243%   $206.8503   $206.85   $206.85   $206.90  
  Purchase #3 $203.94   12.570%   $229.5753   $229.58   $229.60   $229.60  
  Purchase #4 $197.73   5.565%   $208.7337   $208.73   $208.75   $208.70  
  Purchase #5 $244.72   7.826%   $263.8718   $263.87   $263.85   $263.90  
  Purchase #6 $198.29   7.549%   $213.2589   $213.26   $213.25   $213.30  
  Purchase #7 $210.36   13.333%   $238.4073   $238.41   $238.40   $238.40  
  7 purchase totals = $1,422.24       $1,544.9553   $1,544.96   $1,544.95   $1,545.10