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 $232.69   5.600%   $245.7206   $245.72   $245.70   $245.70  
  Purchase #2 $118.69   5.202%   $124.8643   $124.86   $124.85   $124.90  
  Purchase #3 $85.75   8.480%   $93.0216   $93.02   $93.00   $93.00  
  Purchase #4 $21.62   8.558%   $23.4702   $23.47   $23.45   $23.50  
  Purchase #5 $92.97   3.494%   $96.2184   $96.22   $96.20   $96.20  
  Purchase #6 $229.95   6.404%   $244.676   $244.68   $244.70   $244.70  
  Purchase #7 $36.31   11.759%   $40.5797   $40.58   $40.60   $40.60  
  7 purchase totals = $817.98       $868.5508   $868.55   $868.50   $868.60