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	$235.54	6.521%	$250.8996	$250.90	$250.90	$250.90
Purchase #2	$31.55	4.323%	$32.9139	$32.91	$32.90	$32.90
Purchase #3	$214.70	7.245%	$230.255	$230.26	$230.25	$230.30
Purchase #4	$219.27	6.519%	$233.5642	$233.56	$233.55	$233.60
Purchase #5	$134.41	10.316%	$148.2757	$148.28	$148.30	$148.30
Purchase #6	$218.82	6.725%	$233.5356	$233.54	$233.55	$233.50
Purchase #7	$215.57	11.290%	$239.9079	$239.91	$239.90	$239.90
7 purchase totals =	$1,269.86		$1,369.3519	$1,369.36	$1,369.35	$1,369.40