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	$62.96	12.753%	$70.9893	$70.99	$71.00	$71.00
Purchase #2	$123.99	3.828%	$128.7363	$128.74	$128.75	$128.70
Purchase #3	$160.42	7.466%	$172.397	$172.40	$172.40	$172.40
Purchase #4	$12.66	6.245%	$13.4506	$13.45	$13.45	$13.50
Purchase #5	$68.46	12.146%	$76.7752	$76.78	$76.80	$76.80
Purchase #6	$51.58	5.589%	$54.4628	$54.46	$54.45	$54.50
Purchase #7	$130.46	12.127%	$146.2809	$146.28	$146.30	$146.30
7 purchase totals =	$610.53		$663.0921	$663.10	$663.15	$663.20