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	$104.57	6.499%	$111.366	$111.37	$111.35	$111.40
Purchase #2	$164.46	10.219%	$181.2662	$181.27	$181.25	$181.30
Purchase #3	$9.65	5.256%	$10.1572	$10.16	$10.15	$10.20
Purchase #4	$58.51	5.548%	$61.7561	$61.76	$61.75	$61.80
Purchase #5	$163.58	13.183%	$185.1448	$185.14	$185.15	$185.10
Purchase #6	$85.49	4.414%	$89.2635	$89.26	$89.25	$89.30
Purchase #7	$224.74	7.361%	$241.2831	$241.28	$241.30	$241.30
7 purchase totals =	$811.00		$880.2369	$880.24	$880.20	$880.40