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	$82.45	7.478%	$88.6156	$88.62	$88.60	$88.60
Purchase #2	$91.68	9.463%	$100.3557	$100.36	$100.35	$100.40
Purchase #3	$154.32	7.189%	$165.4141	$165.41	$165.40	$165.40
Purchase #4	$164.37	10.344%	$181.3724	$181.37	$181.35	$181.40
Purchase #5	$71.43	3.252%	$73.7529	$73.75	$73.75	$73.80
Purchase #6	$208.27	7.388%	$223.657	$223.66	$223.65	$223.70
Purchase #7	$229.71	7.571%	$247.1013	$247.10	$247.10	$247.10
7 purchase totals =	$1,002.23		$1,080.2690	$1,080.27	$1,080.20	$1,080.40