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	$51.26	8.812%	$55.777	$55.78	$55.80	$55.80
Purchase #2	$98.48	13.205%	$111.4843	$111.48	$111.50	$111.50
Purchase #3	$52.56	6.346%	$55.8955	$55.90	$55.90	$55.90
Purchase #4	$23.94	8.718%	$26.0271	$26.03	$26.05	$26.00
Purchase #5	$240.91	13.243%	$272.8137	$272.81	$272.80	$272.80
Purchase #6	$157.91	4.799%	$165.4881	$165.49	$165.50	$165.50
Purchase #7	$248.67	3.154%	$256.5131	$256.51	$256.50	$256.50
7 purchase totals =	$873.73		$943.9988	$944.00	$944.05	$944.00