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	$209.71	7.493%	$225.4236	$225.42	$225.40	$225.40
Purchase #2	$155.83	12.688%	$175.6017	$175.60	$175.60	$175.60
Purchase #3	$32.52	6.614%	$34.6709	$34.67	$34.65	$34.70
Purchase #4	$18.65	4.425%	$19.4753	$19.48	$19.50	$19.50
Purchase #5	$126.93	3.295%	$131.1123	$131.11	$131.10	$131.10
Purchase #6	$49.78	12.778%	$56.1409	$56.14	$56.15	$56.10
Purchase #7	$114.58	11.330%	$127.5619	$127.56	$127.55	$127.60
7 purchase totals =	$708.00		$769.9866	$769.98	$769.95	$770.00