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	$217.31	11.245%	$241.7465	$241.75	$241.75	$241.70
Purchase #2	$33.92	11.364%	$37.7747	$37.77	$37.75	$37.80
Purchase #3	$153.50	3.843%	$159.399	$159.40	$159.40	$159.40
Purchase #4	$80.64	11.364%	$89.8039	$89.80	$89.80	$89.80
Purchase #5	$183.51	13.258%	$207.8398	$207.84	$207.85	$207.80
Purchase #6	$108.30	11.456%	$120.7068	$120.71	$120.70	$120.70
Purchase #7	$136.28	4.651%	$142.6184	$142.62	$142.60	$142.60
7 purchase totals =	$913.46		$999.8891	$999.89	$999.85	$999.80