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	$68.76	5.451%	$72.5081	$72.51	$72.50	$72.50
Purchase #2	$87.41	4.182%	$91.0655	$91.07	$91.05	$91.10
Purchase #3	$155.89	9.245%	$170.302	$170.30	$170.30	$170.30
Purchase #4	$167.97	10.177%	$185.0643	$185.06	$185.05	$185.10
Purchase #5	$13.79	9.492%	$15.0989	$15.10	$15.10	$15.10
Purchase #6	$129.32	11.385%	$144.0431	$144.04	$144.05	$144.00
Purchase #7	$60.70	7.713%	$65.3818	$65.38	$65.40	$65.40
7 purchase totals =	$683.84		$743.4637	$743.46	$743.45	$743.50