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	$193.55	11.527%	$215.8605	$215.86	$215.85	$215.90
Purchase #2	$56.97	13.668%	$64.7567	$64.76	$64.75	$64.80
Purchase #3	$216.48	11.490%	$241.3536	$241.35	$241.35	$241.40
Purchase #4	$53.58	10.275%	$59.0853	$59.09	$59.10	$59.10
Purchase #5	$75.40	5.449%	$79.5085	$79.51	$79.50	$79.50
Purchase #6	$123.27	4.247%	$128.5053	$128.51	$128.50	$128.50
Purchase #7	$60.38	10.561%	$66.7567	$66.76	$66.75	$66.80
7 purchase totals =	$779.63		$855.8266	$855.84	$855.80	$856.00