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	$152.54	8.590%	$165.6432	$165.64	$165.65	$165.60
Purchase #2	$116.72	4.164%	$121.5802	$121.58	$121.60	$121.60
Purchase #3	$109.85	8.588%	$119.2839	$119.28	$119.30	$119.30
Purchase #4	$33.83	4.203%	$35.2519	$35.25	$35.25	$35.30
Purchase #5	$84.77	6.427%	$90.2182	$90.22	$90.20	$90.20
Purchase #6	$176.43	3.375%	$182.3845	$182.38	$182.40	$182.40
Purchase #7	$53.29	3.745%	$55.2857	$55.29	$55.30	$55.30
7 purchase totals =	$727.43		$769.6476	$769.64	$769.70	$769.70