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	$221.85	10.511%	$245.1687	$245.17	$245.15	$245.20
Purchase #2	$107.71	3.212%	$111.1696	$111.17	$111.15	$111.20
Purchase #3	$208.56	6.793%	$222.7275	$222.73	$222.75	$222.70
Purchase #4	$158.61	6.853%	$169.4795	$169.48	$169.50	$169.50
Purchase #5	$122.45	4.173%	$127.5598	$127.56	$127.55	$127.60
Purchase #6	$127.60	11.365%	$142.1017	$142.10	$142.10	$142.10
Purchase #7	$221.80	8.261%	$240.1229	$240.12	$240.10	$240.10
7 purchase totals =	$1,168.58		$1,258.3297	$1,258.33	$1,258.30	$1,258.40