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	$22.44	9.639%	$24.603	$24.60	$24.60	$24.60
Purchase #2	$158.80	11.274%	$176.7031	$176.70	$176.70	$176.70
Purchase #3	$30.53	4.195%	$31.8107	$31.81	$31.80	$31.80
Purchase #4	$192.50	12.111%	$215.8137	$215.81	$215.80	$215.80
Purchase #5	$124.88	5.173%	$131.34	$131.34	$131.35	$131.30
Purchase #6	$249.61	4.495%	$260.83	$260.83	$260.85	$260.80
Purchase #7	$159.46	4.591%	$166.7808	$166.78	$166.80	$166.80
7 purchase totals =	$938.22		$1,007.8813	$1,007.87	$1,007.90	$1,007.80