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	$19.38	6.381%	$20.6166	$20.62	$20.60	$20.60
Purchase #2	$32.59	9.140%	$35.5687	$35.57	$35.55	$35.60
Purchase #3	$136.89	12.821%	$154.4407	$154.44	$154.45	$154.40
Purchase #4	$211.86	5.151%	$222.7729	$222.77	$222.75	$222.80
Purchase #5	$54.83	9.422%	$59.9961	$60.00	$60.00	$60.00
Purchase #6	$50.88	9.811%	$55.8718	$55.87	$55.85	$55.90
Purchase #7	$168.39	5.379%	$177.4477	$177.45	$177.45	$177.40
7 purchase totals =	$674.82		$726.7145	$726.72	$726.65	$726.70