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	$218.30	12.577%	$245.7556	$245.76	$245.75	$245.80
Purchase #2	$216.94	6.802%	$231.6963	$231.70	$231.70	$231.70
Purchase #3	$56.72	8.433%	$61.5032	$61.50	$61.50	$61.50
Purchase #4	$123.88	4.539%	$129.5029	$129.50	$129.50	$129.50
Purchase #5	$113.50	11.511%	$126.565	$126.57	$126.55	$126.60
Purchase #6	$172.28	4.273%	$179.6415	$179.64	$179.65	$179.60
Purchase #7	$100.94	10.118%	$111.1531	$111.15	$111.15	$111.20
7 purchase totals =	$1,002.56		$1,085.8176	$1,085.82	$1,085.80	$1,085.90