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 $217.70   7.514%   $234.058   $234.06   $234.05   $234.10  
  Purchase #2 $41.69   8.276%   $45.1403   $45.14   $45.15   $45.10  
  Purchase #3 $25.91   7.865%   $27.9478   $27.95   $27.95   $27.90  
  Purchase #4 $157.99   6.513%   $168.2799   $168.28   $168.30   $168.30  
  Purchase #5 $204.76   3.547%   $212.0228   $212.02   $212.00   $212.00  
  Purchase #6 $109.87   10.142%   $121.013   $121.01   $121.00   $121.00  
  Purchase #7 $199.55   12.447%   $224.388   $224.39   $224.40   $224.40  
  7 purchase totals = $957.47       $1,032.8498   $1,032.85   $1,032.85   $1,032.80