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	$162.92	5.253%	$171.4782	$171.48	$171.50	$171.50
Purchase #2	$49.80	13.671%	$56.6082	$56.61	$56.60	$56.60
Purchase #3	$211.28	10.322%	$233.0883	$233.09	$233.10	$233.10
Purchase #4	$249.54	11.395%	$277.9751	$277.98	$278.00	$278.00
Purchase #5	$67.42	4.591%	$70.5153	$70.52	$70.50	$70.50
Purchase #6	$229.43	11.611%	$256.0691	$256.07	$256.05	$256.10
Purchase #7	$5.33	4.249%	$5.5565	$5.56	$5.55	$5.60
7 purchase totals =	$975.72		$1,071.2907	$1,071.31	$1,071.30	$1,071.40