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	$233.33	3.684%	$241.9259	$241.93	$241.95	$241.90
Purchase #2	$137.63	10.638%	$152.2711	$152.27	$152.25	$152.30
Purchase #3	$165.47	4.180%	$172.3866	$172.39	$172.40	$172.40
Purchase #4	$230.83	10.386%	$254.804	$254.80	$254.80	$254.80
Purchase #5	$233.91	10.189%	$257.7431	$257.74	$257.75	$257.70
Purchase #6	$37.46	3.434%	$38.7464	$38.75	$38.75	$38.70
Purchase #7	$176.25	5.178%	$185.3762	$185.38	$185.40	$185.40
7 purchase totals =	$1,214.88		$1,303.2533	$1,303.26	$1,303.30	$1,303.20