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 $69.26   4.391%   $72.3012   $72.30   $72.30   $72.30  
  Purchase #2 $70.85   6.418%   $75.3972   $75.40   $75.40   $75.40  
  Purchase #3 $13.32   6.600%   $14.1991   $14.20   $14.20   $14.20  
  Purchase #4 $119.55   8.833%   $130.1099   $130.11   $130.10   $130.10  
  Purchase #5 $140.84   3.548%   $145.837   $145.84   $145.85   $145.80  
  Purchase #6 $33.33   3.374%   $34.4546   $34.45   $34.45   $34.50  
  Purchase #7 $226.50   6.856%   $242.0288   $242.03   $242.05   $242.00  
  7 purchase totals = $673.65       $714.3278   $714.33   $714.35   $714.30