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	$52.37	7.449%	$56.271	$56.27	$56.25	$56.30
Purchase #2	$141.98	6.760%	$151.5778	$151.58	$151.60	$151.60
Purchase #3	$137.57	3.106%	$141.8429	$141.84	$141.85	$141.80
Purchase #4	$46.39	8.636%	$50.3962	$50.40	$50.40	$50.40
Purchase #5	$36.99	8.479%	$40.1264	$40.13	$40.15	$40.10
Purchase #6	$81.93	4.820%	$85.879	$85.88	$85.90	$85.90
Purchase #7	$180.63	12.730%	$203.6242	$203.62	$203.60	$203.60
7 purchase totals =	$677.86		$729.7175	$729.72	$729.75	$729.70