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	$160.41	7.511%	$172.4584	$172.46	$172.45	$172.50
Purchase #2	$179.63	7.249%	$192.6514	$192.65	$192.65	$192.70
Purchase #3	$34.42	10.107%	$37.8988	$37.90	$37.90	$37.90
Purchase #4	$159.36	6.305%	$169.4076	$169.41	$169.40	$169.40
Purchase #5	$169.71	13.474%	$192.5767	$192.58	$192.60	$192.60
Purchase #6	$99.57	12.415%	$111.9316	$111.93	$111.95	$111.90
Purchase #7	$216.40	4.707%	$226.5859	$226.59	$226.60	$226.60
7 purchase totals =	$1,019.50		$1,103.5104	$1,103.52	$1,103.55	$1,103.60