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	$191.29	8.391%	$207.3411	$207.34	$207.35	$207.30
Purchase #2	$112.76	9.870%	$123.8894	$123.89	$123.90	$123.90
Purchase #3	$108.39	7.568%	$116.593	$116.59	$116.60	$116.60
Purchase #4	$144.95	8.415%	$157.1475	$157.15	$157.15	$157.10
Purchase #5	$164.50	5.290%	$173.2021	$173.20	$173.20	$173.20
Purchase #6	$98.87	12.840%	$111.5649	$111.56	$111.55	$111.60
Purchase #7	$102.66	3.125%	$105.8681	$105.87	$105.85	$105.90
7 purchase totals =	$923.42		$995.6061	$995.60	$995.60	$995.60