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	$230.44	3.187%	$237.7841	$237.78	$237.80	$237.80
Purchase #2	$104.51	11.173%	$116.1869	$116.19	$116.20	$116.20
Purchase #3	$80.96	7.796%	$87.2716	$87.27	$87.25	$87.30
Purchase #4	$223.37	7.671%	$240.5047	$240.50	$240.50	$240.50
Purchase #5	$99.47	12.355%	$111.7595	$111.76	$111.75	$111.80
Purchase #6	$194.77	10.162%	$214.5625	$214.56	$214.55	$214.60
Purchase #7	$127.52	11.119%	$141.6989	$141.70	$141.70	$141.70
7 purchase totals =	$1,061.04		$1,149.7682	$1,149.76	$1,149.75	$1,149.90