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 $32.76   5.787%   $34.6558   $34.66   $34.65   $34.70  
  Purchase #2 $225.39   5.188%   $237.0832   $237.08   $237.10   $237.10  
  Purchase #3 $9.35   11.170%   $10.3944   $10.39   $10.40   $10.40  
  Purchase #4 $160.41   5.868%   $169.8229   $169.82   $169.80   $169.80  
  Purchase #5 $221.80   6.682%   $236.6207   $236.62   $236.60   $236.60  
  Purchase #6 $175.56   10.706%   $194.3555   $194.36   $194.35   $194.40  
  Purchase #7 $152.73   3.690%   $158.3657   $158.37   $158.35   $158.40  
  7 purchase totals = $978.00       $1,041.2982   $1,041.30   $1,041.25   $1,041.40