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 $200.31   10.703%   $221.7492   $221.75   $221.75   $221.70  
  Purchase #2 $211.98   10.866%   $235.0137   $235.01   $235.00   $235.00  
  Purchase #3 $153.96   12.588%   $173.3405   $173.34   $173.35   $173.30  
  Purchase #4 $30.53   11.421%   $34.0168   $34.02   $34.00   $34.00  
  Purchase #5 $241.57   8.838%   $262.92   $262.92   $262.90   $262.90  
  Purchase #6 $47.66   6.677%   $50.8423   $50.84   $50.85   $50.80  
  Purchase #7 $41.68   13.434%   $47.2793   $47.28   $47.30   $47.30  
  7 purchase totals = $927.69       $1,025.1618   $1,025.16   $1,025.15   $1,025.00