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 $60.53   4.389%   $63.1867   $63.19   $63.20   $63.20  
  Purchase #2 $73.32   11.844%   $82.004   $82.00   $82.00   $82.00  
  Purchase #3 $33.68   3.283%   $34.7857   $34.79   $34.80   $34.80  
  Purchase #4 $39.68   5.560%   $41.8862   $41.89   $41.90   $41.90  
  Purchase #5 $192.42   6.472%   $204.8734   $204.87   $204.85   $204.90  
  Purchase #6 $174.28   12.143%   $195.4428   $195.44   $195.45   $195.40  
  Purchase #7 $128.51   10.834%   $142.4328   $142.43   $142.45   $142.40  
  7 purchase totals = $702.42       $764.6116   $764.61   $764.65   $764.60