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 $62.46   11.196%   $69.453   $69.45   $69.45   $69.50  
  Purchase #2 $30.38   13.436%   $34.4619   $34.46   $34.45   $34.50  
  Purchase #3 $207.84   10.636%   $229.9459   $229.95   $229.95   $229.90  
  Purchase #4 $185.65   4.175%   $193.4009   $193.40   $193.40   $193.40  
  Purchase #5 $225.44   12.560%   $253.7553   $253.76   $253.75   $253.80  
  Purchase #6 $201.71   5.243%   $212.2857   $212.29   $212.30   $212.30  
  Purchase #7 $197.94   6.507%   $210.82   $210.82   $210.80   $210.80  
  7 purchase totals = $1,111.42       $1,204.1227   $1,204.13   $1,204.10   $1,204.20