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	$32.30	4.243%	$33.6705	$33.67	$33.65	$33.70
Purchase #2	$217.72	3.386%	$225.092	$225.09	$225.10	$225.10
Purchase #3	$23.80	13.728%	$27.0673	$27.07	$27.05	$27.10
Purchase #4	$160.68	7.680%	$173.0202	$173.02	$173.00	$173.00
Purchase #5	$54.71	11.784%	$61.157	$61.16	$61.15	$61.20
Purchase #6	$206.27	5.259%	$217.1177	$217.12	$217.10	$217.10
Purchase #7	$42.89	9.326%	$46.8899	$46.89	$46.90	$46.90
7 purchase totals =	$738.37		$784.0146	$784.02	$783.95	$784.10