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 $214.51   8.825%   $233.4405   $233.44   $233.45   $233.40  
  Purchase #2 $150.46   8.722%   $163.5831   $163.58   $163.60   $163.60  
  Purchase #3 $22.86   5.772%   $24.1795   $24.18   $24.20   $24.20  
  Purchase #4 $160.72   9.377%   $175.7907   $175.79   $175.80   $175.80  
  Purchase #5 $215.60   11.799%   $241.0386   $241.04   $241.05   $241.00  
  Purchase #6 $237.79   5.197%   $250.1479   $250.15   $250.15   $250.10  
  Purchase #7 $205.52   11.510%   $229.1754   $229.18   $229.20   $229.20  
  7 purchase totals = $1,207.46       $1,317.3557   $1,317.36   $1,317.45   $1,317.30