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 $85.83   7.396%   $92.178   $92.18   $92.20   $92.20  
  Purchase #2 $237.74   6.807%   $253.923   $253.92   $253.90   $253.90  
  Purchase #3 $116.36   9.612%   $127.5445   $127.54   $127.55   $127.50  
  Purchase #4 $234.86   7.397%   $252.2326   $252.23   $252.25   $252.20  
  Purchase #5 $29.78   8.318%   $32.2571   $32.26   $32.25   $32.30  
  Purchase #6 $116.97   7.203%   $125.3953   $125.40   $125.40   $125.40  
  Purchase #7 $120.28   5.165%   $126.4925   $126.49   $126.50   $126.50  
  7 purchase totals = $941.82       $1,010.0230   $1,010.02   $1,010.05   $1,010.00