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	$85.43	4.707%	$89.4512	$89.45	$89.45	$89.50
Purchase #2	$158.52	9.613%	$173.7585	$173.76	$173.75	$173.80
Purchase #3	$138.38	7.279%	$148.4527	$148.45	$148.45	$148.50
Purchase #4	$61.36	9.802%	$67.3745	$67.37	$67.35	$67.40
Purchase #5	$84.81	10.605%	$93.8041	$93.80	$93.80	$93.80
Purchase #6	$89.74	13.805%	$102.1286	$102.13	$102.15	$102.10
Purchase #7	$141.94	4.388%	$148.1683	$148.17	$148.15	$148.20
7 purchase totals =	$760.18		$823.1379	$823.13	$823.10	$823.30