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	$241.61	4.823%	$253.2629	$253.26	$253.25	$253.30
Purchase #2	$85.80	11.650%	$95.7957	$95.80	$95.80	$95.80
Purchase #3	$241.40	5.333%	$254.2739	$254.27	$254.25	$254.30
Purchase #4	$98.51	7.234%	$105.6362	$105.64	$105.65	$105.60
Purchase #5	$116.83	12.563%	$131.5074	$131.51	$131.50	$131.50
Purchase #6	$28.28	3.769%	$29.3459	$29.35	$29.35	$29.30
Purchase #7	$146.65	3.420%	$151.6654	$151.67	$151.65	$151.70
7 purchase totals =	$959.08		$1,021.4874	$1,021.50	$1,021.45	$1,021.50