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	$146.72	4.654%	$153.5483	$153.55	$153.55	$153.50
Purchase #2	$102.73	13.716%	$116.8204	$116.82	$116.80	$116.80
Purchase #3	$250.65	4.510%	$261.9543	$261.95	$261.95	$262.00
Purchase #4	$228.25	5.346%	$240.4522	$240.45	$240.45	$240.50
Purchase #5	$200.98	9.755%	$220.5856	$220.59	$220.60	$220.60
Purchase #6	$236.47	3.364%	$244.4249	$244.42	$244.40	$244.40
Purchase #7	$157.92	9.453%	$172.8482	$172.85	$172.85	$172.80
7 purchase totals =	$1,323.72		$1,410.6339	$1,410.63	$1,410.60	$1,410.60