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 $214.94   8.522%   $233.2572   $233.26   $233.25   $233.30  
  Purchase #2 $116.84   10.623%   $129.2519   $129.25   $129.25   $129.30  
  Purchase #3 $45.61   5.194%   $47.979   $47.98   $48.00   $48.00  
  Purchase #4 $189.63   3.742%   $196.726   $196.73   $196.75   $196.70  
  Purchase #5 $38.74   6.151%   $41.1229   $41.12   $41.10   $41.10  
  Purchase #6 $185.58   8.750%   $201.8183   $201.82   $201.80   $201.80  
  Purchase #7 $148.62   11.722%   $166.0412   $166.04   $166.05   $166.00  
  7 purchase totals = $939.96       $1,016.1965   $1,016.20   $1,016.20   $1,016.20