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	$68.33	8.751%	$74.3096	$74.31	$74.30	$74.30
Purchase #2	$76.50	5.245%	$80.5124	$80.51	$80.50	$80.50
Purchase #3	$172.76	3.853%	$179.4164	$179.42	$179.40	$179.40
Purchase #4	$207.77	11.219%	$231.0797	$231.08	$231.10	$231.10
Purchase #5	$145.72	11.581%	$162.5958	$162.60	$162.60	$162.60
Purchase #6	$155.53	4.485%	$162.5055	$162.51	$162.50	$162.50
Purchase #7	$76.34	3.356%	$78.902	$78.90	$78.90	$78.90
7 purchase totals =	$902.95		$969.3214	$969.33	$969.30	$969.30