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 $92.79   3.772%   $96.29   $96.29   $96.30   $96.30  
  Purchase #2 $213.63   6.494%   $227.5031   $227.50   $227.50   $227.50  
  Purchase #3 $61.52   10.673%   $68.086   $68.09   $68.10   $68.10  
  Purchase #4 $134.49   3.829%   $139.6396   $139.64   $139.65   $139.60  
  Purchase #5 $47.87   13.766%   $54.4598   $54.46   $54.45   $54.50  
  Purchase #6 $215.58   12.146%   $241.7643   $241.76   $241.75   $241.80  
  Purchase #7 $175.37   4.119%   $182.5935   $182.59   $182.60   $182.60  
  7 purchase totals = $941.25       $1,010.3363   $1,010.33   $1,010.35   $1,010.40