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	$240.33	12.105%	$269.4219	$269.42	$269.40	$269.40
Purchase #2	$92.71	13.603%	$105.3213	$105.32	$105.30	$105.30
Purchase #3	$139.28	6.479%	$148.304	$148.30	$148.30	$148.30
Purchase #4	$100.47	13.747%	$114.2816	$114.28	$114.30	$114.30
Purchase #5	$173.95	12.519%	$195.7268	$195.73	$195.75	$195.70
Purchase #6	$112.74	5.335%	$118.7547	$118.75	$118.75	$118.80
Purchase #7	$136.74	12.151%	$153.3553	$153.36	$153.35	$153.40
7 purchase totals =	$996.22		$1,105.1656	$1,105.16	$1,105.15	$1,105.20