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 $69.51   7.844%   $74.9624   $74.96   $74.95   $75.00  
  Purchase #2 $237.39   7.141%   $254.342   $254.34   $254.35   $254.30  
  Purchase #3 $97.68   10.384%   $107.8231   $107.82   $107.80   $107.80  
  Purchase #4 $149.65   12.282%   $168.03   $168.03   $168.05   $168.00  
  Purchase #5 $56.58   7.522%   $60.8359   $60.84   $60.85   $60.80  
  Purchase #6 $21.98   3.274%   $22.6996   $22.70   $22.70   $22.70  
  Purchase #7 $198.63   7.122%   $212.7764   $212.78   $212.80   $212.80  
  7 purchase totals = $831.42       $901.4694   $901.47   $901.50   $901.40