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	$147.80	11.753%	$165.1709	$165.17	$165.15	$165.20
Purchase #2	$248.42	6.574%	$264.7511	$264.75	$264.75	$264.80
Purchase #3	$83.39	8.351%	$90.3539	$90.35	$90.35	$90.40
Purchase #4	$110.99	13.656%	$126.1468	$126.15	$126.15	$126.10
Purchase #5	$242.28	4.741%	$253.7665	$253.77	$253.75	$253.80
Purchase #6	$132.71	6.371%	$141.165	$141.17	$141.15	$141.20
Purchase #7	$62.70	12.662%	$70.6391	$70.64	$70.65	$70.60
7 purchase totals =	$1,028.29		$1,111.9933	$1,112.00	$1,111.95	$1,112.10