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 $208.63   8.232%   $225.8044   $225.80   $225.80   $225.80  
  Purchase #2 $136.63   5.621%   $144.31   $144.31   $144.30   $144.30  
  Purchase #3 $157.71   7.760%   $169.9483   $169.95   $169.95   $169.90  
  Purchase #4 $199.93   8.668%   $217.2599   $217.26   $217.25   $217.30  
  Purchase #5 $29.55   10.539%   $32.6643   $32.66   $32.65   $32.70  
  Purchase #6 $129.97   11.574%   $145.0127   $145.01   $145.00   $145.00  
  Purchase #7 $162.92   11.475%   $181.6151   $181.62   $181.60   $181.60  
  7 purchase totals = $1,025.34       $1,116.6147   $1,116.61   $1,116.55   $1,116.60