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	$62.94	11.531%	$70.1976	$70.20	$70.20	$70.20
Purchase #2	$243.98	11.148%	$271.1789	$271.18	$271.20	$271.20
Purchase #3	$55.27	6.606%	$58.9211	$58.92	$58.90	$58.90
Purchase #4	$168.95	3.559%	$174.9629	$174.96	$174.95	$175.00
Purchase #5	$83.93	13.710%	$95.4368	$95.44	$95.45	$95.40
Purchase #6	$112.42	13.317%	$127.391	$127.39	$127.40	$127.40
Purchase #7	$105.47	5.703%	$111.485	$111.49	$111.50	$111.50
7 purchase totals =	$832.96		$909.5733	$909.58	$909.60	$909.60