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	$158.73	4.131%	$165.2871	$165.29	$165.30	$165.30
Purchase #2	$179.56	9.466%	$196.5571	$196.56	$196.55	$196.60
Purchase #3	$161.46	3.105%	$166.4733	$166.47	$166.45	$166.50
Purchase #4	$197.75	3.668%	$205.0035	$205.00	$205.00	$205.00
Purchase #5	$32.55	8.402%	$35.2849	$35.28	$35.30	$35.30
Purchase #6	$185.29	4.520%	$193.6651	$193.67	$193.65	$193.70
Purchase #7	$85.80	5.175%	$90.2402	$90.24	$90.25	$90.20
7 purchase totals =	$1,001.14		$1,052.5112	$1,052.51	$1,052.50	$1,052.60