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	$119.34	6.867%	$127.5351	$127.54	$127.55	$127.50
Purchase #2	$72.86	7.499%	$78.3238	$78.32	$78.30	$78.30
Purchase #3	$93.68	13.452%	$106.2818	$106.28	$106.30	$106.30
Purchase #4	$218.48	11.554%	$243.7232	$243.72	$243.70	$243.70
Purchase #5	$230.96	9.316%	$252.4762	$252.48	$252.50	$252.50
Purchase #6	$177.91	4.235%	$185.4445	$185.44	$185.45	$185.40
Purchase #7	$198.60	9.186%	$216.8434	$216.84	$216.85	$216.80
7 purchase totals =	$1,111.83		$1,210.6280	$1,210.62	$1,210.65	$1,210.50