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 $71.44   7.258%   $76.6251   $76.63   $76.65   $76.60  
  Purchase #2 $102.34   7.789%   $110.3113   $110.31   $110.30   $110.30  
  Purchase #3 $75.89   8.546%   $82.3756   $82.38   $82.40   $82.40  
  Purchase #4 $97.47   5.647%   $102.9741   $102.97   $102.95   $103.00  
  Purchase #5 $200.73   7.232%   $215.2468   $215.25   $215.25   $215.20  
  Purchase #6 $192.35   13.663%   $218.6308   $218.63   $218.65   $218.60  
  Purchase #7 $129.91   10.702%   $143.813   $143.81   $143.80   $143.80  
  7 purchase totals = $870.13       $949.9767   $949.98   $950.00   $949.90