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	$96.26	4.466%	$100.559	$100.56	$100.55	$100.60
Purchase #2	$127.28	12.469%	$143.1505	$143.15	$143.15	$143.20
Purchase #3	$58.30	4.869%	$61.1386	$61.14	$61.15	$61.10
Purchase #4	$112.89	11.783%	$126.1918	$126.19	$126.20	$126.20
Purchase #5	$214.31	11.300%	$238.527	$238.53	$238.55	$238.50
Purchase #6	$47.43	3.327%	$49.008	$49.01	$49.00	$49.00
Purchase #7	$32.30	5.674%	$34.1327	$34.13	$34.15	$34.10
7 purchase totals =	$688.77		$752.7076	$752.71	$752.75	$752.70