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	$166.68	5.489%	$175.8291	$175.83	$175.85	$175.80
Purchase #2	$97.83	7.808%	$105.4686	$105.47	$105.45	$105.50
Purchase #3	$100.32	9.282%	$109.6317	$109.63	$109.65	$109.60
Purchase #4	$128.60	13.514%	$145.979	$145.98	$146.00	$146.00
Purchase #5	$178.51	4.797%	$187.0731	$187.07	$187.05	$187.10
Purchase #6	$34.58	4.459%	$36.1219	$36.12	$36.10	$36.10
Purchase #7	$83.67	5.793%	$88.517	$88.52	$88.50	$88.50
7 purchase totals =	$790.19		$848.6204	$848.62	$848.60	$848.60