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	$205.25	5.460%	$216.4567	$216.46	$216.45	$216.50
Purchase #2	$40.27	9.183%	$43.968	$43.97	$43.95	$44.00
Purchase #3	$46.64	8.530%	$50.6184	$50.62	$50.60	$50.60
Purchase #4	$90.75	6.315%	$96.4809	$96.48	$96.50	$96.50
Purchase #5	$59.33	11.455%	$66.1263	$66.13	$66.15	$66.10
Purchase #6	$18.51	11.301%	$20.6018	$20.60	$20.60	$20.60
Purchase #7	$189.95	10.599%	$210.0828	$210.08	$210.10	$210.10
7 purchase totals =	$650.70		$704.3349	$704.34	$704.35	$704.40