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 $33.63   3.259%   $34.726   $34.73   $34.75   $34.70  
  Purchase #2 $246.70   7.737%   $265.7872   $265.79   $265.80   $265.80  
  Purchase #3 $150.98   11.843%   $168.8606   $168.86   $168.85   $168.90  
  Purchase #4 $20.69   9.486%   $22.6527   $22.65   $22.65   $22.70  
  Purchase #5 $246.33   8.449%   $267.1424   $267.14   $267.15   $267.10  
  Purchase #6 $129.71   4.780%   $135.9101   $135.91   $135.90   $135.90  
  Purchase #7 $212.87   4.710%   $222.8962   $222.90   $222.90   $222.90  
  7 purchase totals = $1,040.91       $1,117.9752   $1,117.98   $1,118.00   $1,118.00