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	$65.34	11.117%	$72.6038	$72.60	$72.60	$72.60
Purchase #2	$50.55	10.772%	$55.9952	$56.00	$56.00	$56.00
Purchase #3	$75.31	10.810%	$83.451	$83.45	$83.45	$83.50
Purchase #4	$93.52	6.790%	$99.87	$99.87	$99.85	$99.90
Purchase #5	$76.57	7.185%	$82.0716	$82.07	$82.05	$82.10
Purchase #6	$26.82	12.430%	$30.1537	$30.15	$30.15	$30.20
Purchase #7	$211.45	9.642%	$231.838	$231.84	$231.85	$231.80
7 purchase totals =	$599.56		$655.9833	$655.98	$655.95	$656.10