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	$130.87	13.642%	$148.7233	$148.72	$148.70	$148.70
Purchase #2	$113.51	8.757%	$123.4501	$123.45	$123.45	$123.50
Purchase #3	$76.79	3.555%	$79.5199	$79.52	$79.50	$79.50
Purchase #4	$131.87	11.736%	$147.3463	$147.35	$147.35	$147.30
Purchase #5	$193.82	7.170%	$207.7169	$207.72	$207.70	$207.70
Purchase #6	$244.37	5.636%	$258.1427	$258.14	$258.15	$258.10
Purchase #7	$123.33	3.570%	$127.7329	$127.73	$127.75	$127.70
7 purchase totals =	$1,014.56		$1,092.6321	$1,092.63	$1,092.60	$1,092.50