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	$134.91	13.584%	$153.2362	$153.24	$153.25	$153.20
Purchase #2	$221.89	11.397%	$247.1788	$247.18	$247.20	$247.20
Purchase #3	$247.33	3.158%	$255.1407	$255.14	$255.15	$255.10
Purchase #4	$209.60	13.562%	$238.026	$238.03	$238.05	$238.00
Purchase #5	$159.88	10.591%	$176.8129	$176.81	$176.80	$176.80
Purchase #6	$84.71	11.548%	$94.4923	$94.49	$94.50	$94.50
Purchase #7	$31.90	4.808%	$33.4338	$33.43	$33.45	$33.40
7 purchase totals =	$1,090.22		$1,198.3207	$1,198.32	$1,198.40	$1,198.20