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	$144.46	4.534%	$151.0098	$151.01	$151.00	$151.00
Purchase #2	$61.89	7.681%	$66.6438	$66.64	$66.65	$66.60
Purchase #3	$62.76	11.424%	$69.9297	$69.93	$69.95	$69.90
Purchase #4	$221.68	10.393%	$244.7192	$244.72	$244.70	$244.70
Purchase #5	$100.45	5.697%	$106.1726	$106.17	$106.15	$106.20
Purchase #6	$221.52	11.623%	$247.2673	$247.27	$247.25	$247.30
Purchase #7	$227.60	12.748%	$256.6144	$256.61	$256.60	$256.60
7 purchase totals =	$1,040.36		$1,142.3568	$1,142.35	$1,142.30	$1,142.30