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 $85.46   7.608%   $91.9618   $91.96   $91.95   $92.00  
  Purchase #2 $217.43   13.346%   $246.4482   $246.45   $246.45   $246.40  
  Purchase #3 $232.90   5.269%   $245.1715   $245.17   $245.15   $245.20  
  Purchase #4 $53.54   9.747%   $58.7585   $58.76   $58.75   $58.80  
  Purchase #5 $150.86   7.829%   $162.6708   $162.67   $162.65   $162.70  
  Purchase #6 $207.26   5.656%   $218.9826   $218.98   $219.00   $219.00  
  Purchase #7 $107.82   7.773%   $116.2008   $116.20   $116.20   $116.20  
  7 purchase totals = $1,055.27       $1,140.1942   $1,140.19   $1,140.15   $1,140.30