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	$40.39	8.222%	$43.7109	$43.71	$43.70	$43.70
Purchase #2	$39.68	7.445%	$42.6342	$42.63	$42.65	$42.60
Purchase #3	$81.60	12.155%	$91.5185	$91.52	$91.50	$91.50
Purchase #4	$112.53	9.398%	$123.1056	$123.11	$123.10	$123.10
Purchase #5	$159.49	11.838%	$178.3704	$178.37	$178.35	$178.40
Purchase #6	$175.57	13.643%	$199.523	$199.52	$199.50	$199.50
Purchase #7	$50.79	7.816%	$54.7597	$54.76	$54.75	$54.80
7 purchase totals =	$660.05		$733.6223	$733.62	$733.55	$733.60