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	$178.95	3.719%	$185.6052	$185.61	$185.60	$185.60
Purchase #2	$25.91	13.572%	$29.4265	$29.43	$29.45	$29.40
Purchase #3	$178.30	3.844%	$185.1539	$185.15	$185.15	$185.20
Purchase #4	$122.27	12.674%	$137.7665	$137.77	$137.75	$137.80
Purchase #5	$80.73	8.109%	$87.2764	$87.28	$87.30	$87.30
Purchase #6	$55.82	9.158%	$60.932	$60.93	$60.95	$60.90
Purchase #7	$46.63	3.668%	$48.3404	$48.34	$48.35	$48.30
7 purchase totals =	$688.61		$734.5009	$734.51	$734.55	$734.50