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	$137.72	5.642%	$145.4902	$145.49	$145.50	$145.50
Purchase #2	$82.55	3.533%	$85.4665	$85.47	$85.45	$85.50
Purchase #3	$145.52	10.857%	$161.3191	$161.32	$161.30	$161.30
Purchase #4	$249.98	11.609%	$279.0002	$279.00	$279.00	$279.00
Purchase #5	$239.89	3.627%	$248.5908	$248.59	$248.60	$248.60
Purchase #6	$87.29	4.362%	$91.0976	$91.10	$91.10	$91.10
Purchase #7	$10.78	3.573%	$11.1652	$11.17	$11.15	$11.20
7 purchase totals =	$953.73		$1,022.1296	$1,022.14	$1,022.10	$1,022.20