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	$218.63	10.849%	$242.3492	$242.35	$242.35	$242.30
Purchase #2	$172.33	5.115%	$181.1447	$181.14	$181.15	$181.10
Purchase #3	$187.51	10.518%	$207.2323	$207.23	$207.25	$207.20
Purchase #4	$61.50	5.393%	$64.8167	$64.82	$64.80	$64.80
Purchase #5	$101.62	9.842%	$111.6214	$111.62	$111.60	$111.60
Purchase #6	$229.32	6.520%	$244.2717	$244.27	$244.25	$244.30
Purchase #7	$216.70	3.259%	$223.7623	$223.76	$223.75	$223.80
7 purchase totals =	$1,187.61		$1,275.1983	$1,275.19	$1,275.15	$1,275.10