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	$169.67	8.692%	$184.4177	$184.42	$184.40	$184.40
Purchase #2	$131.59	13.668%	$149.5757	$149.58	$149.60	$149.60
Purchase #3	$102.36	8.693%	$111.2582	$111.26	$111.25	$111.30
Purchase #4	$216.98	11.219%	$241.323	$241.32	$241.30	$241.30
Purchase #5	$48.66	9.210%	$53.1416	$53.14	$53.15	$53.10
Purchase #6	$213.61	8.474%	$231.7113	$231.71	$231.70	$231.70
Purchase #7	$99.86	3.300%	$103.1554	$103.16	$103.15	$103.20
7 purchase totals =	$982.73		$1,074.5829	$1,074.59	$1,074.55	$1,074.60