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 $217.61   8.325%   $235.726   $235.73   $235.75   $235.70  
  Purchase #2 $156.79   5.674%   $165.6863   $165.69   $165.70   $165.70  
  Purchase #3 $137.53   8.186%   $148.7882   $148.79   $148.80   $148.80  
  Purchase #4 $139.45   4.611%   $145.88   $145.88   $145.90   $145.90  
  Purchase #5 $23.73   7.148%   $25.4262   $25.43   $25.45   $25.40  
  Purchase #6 $116.63   10.583%   $128.973   $128.97   $128.95   $129.00  
  Purchase #7 $240.60   9.748%   $264.0537   $264.05   $264.05   $264.10  
  7 purchase totals = $1,032.34       $1,114.5334   $1,114.54   $1,114.60   $1,114.60