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	$160.62	7.521%	$172.7002	$172.70	$172.70	$172.70
Purchase #2	$109.89	4.366%	$114.6878	$114.69	$114.70	$114.70
Purchase #3	$235.98	11.564%	$263.2687	$263.27	$263.25	$263.30
Purchase #4	$126.56	11.802%	$141.4966	$141.50	$141.50	$141.50
Purchase #5	$67.77	5.132%	$71.248	$71.25	$71.25	$71.20
Purchase #6	$149.62	7.826%	$161.3293	$161.33	$161.35	$161.30
Purchase #7	$247.47	6.864%	$264.4563	$264.46	$264.45	$264.50
7 purchase totals =	$1,097.91		$1,189.1869	$1,189.20	$1,189.20	$1,189.20