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	$74.26	3.152%	$76.6007	$76.60	$76.60	$76.60
Purchase #2	$139.77	12.203%	$156.8261	$156.83	$156.85	$156.80
Purchase #3	$173.46	11.574%	$193.5363	$193.54	$193.55	$193.50
Purchase #4	$246.27	10.519%	$272.1751	$272.18	$272.20	$272.20
Purchase #5	$146.47	10.771%	$162.2463	$162.25	$162.25	$162.20
Purchase #6	$71.75	4.417%	$74.9192	$74.92	$74.90	$74.90
Purchase #7	$243.58	4.740%	$255.1257	$255.13	$255.15	$255.10
7 purchase totals =	$1,095.56		$1,191.4294	$1,191.45	$1,191.50	$1,191.30