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	$217.49	4.428%	$227.1205	$227.12	$227.10	$227.10
Purchase #2	$111.64	11.563%	$124.5489	$124.55	$124.55	$124.50
Purchase #3	$167.63	10.487%	$185.2094	$185.21	$185.20	$185.20
Purchase #4	$172.39	9.291%	$188.4068	$188.41	$188.40	$188.40
Purchase #5	$173.72	4.712%	$181.9057	$181.91	$181.90	$181.90
Purchase #6	$211.77	5.440%	$223.2903	$223.29	$223.30	$223.30
Purchase #7	$150.32	6.188%	$159.6218	$159.62	$159.60	$159.60
7 purchase totals =	$1,204.96		$1,290.1034	$1,290.11	$1,290.05	$1,290.00