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 $182.71   10.743%   $202.3385   $202.34   $202.35   $202.30  
  Purchase #2 $117.94   12.586%   $132.7839   $132.78   $132.80   $132.80  
  Purchase #3 $113.91   12.401%   $128.036   $128.04   $128.05   $128.00  
  Purchase #4 $218.57   6.683%   $233.177   $233.18   $233.20   $233.20  
  Purchase #5 $12.36   5.147%   $12.9962   $13.00   $13.00   $13.00  
  Purchase #6 $156.53   11.800%   $175.0005   $175.00   $175.00   $175.00  
  Purchase #7 $163.75   12.355%   $183.9813   $183.98   $184.00   $184.00  
  7 purchase totals = $965.77       $1,068.3134   $1,068.32   $1,068.40   $1,068.30