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 $182.60   13.224%   $206.747   $206.75   $206.75   $206.70  
  Purchase #2 $179.64   12.117%   $201.407   $201.41   $201.40   $201.40  
  Purchase #3 $16.72   9.478%   $18.3047   $18.30   $18.30   $18.30  
  Purchase #4 $119.42   5.337%   $125.7934   $125.79   $125.80   $125.80  
  Purchase #5 $155.65   6.833%   $166.2856   $166.29   $166.30   $166.30  
  Purchase #6 $65.76   11.502%   $73.3237   $73.32   $73.30   $73.30  
  Purchase #7 $75.72   10.580%   $83.7312   $83.73   $83.75   $83.70  
  7 purchase totals = $795.51       $875.5926   $875.59   $875.60   $875.50