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	$61.87	3.835%	$64.2427	$64.24	$64.25	$64.20
Purchase #2	$71.99	9.215%	$78.6239	$78.62	$78.60	$78.60
Purchase #3	$25.96	8.115%	$28.0667	$28.07	$28.05	$28.10
Purchase #4	$92.42	12.130%	$103.6305	$103.63	$103.65	$103.60
Purchase #5	$26.38	5.420%	$27.8098	$27.81	$27.80	$27.80
Purchase #6	$150.83	13.808%	$171.6566	$171.66	$171.65	$171.70
Purchase #7	$16.49	10.600%	$18.2379	$18.24	$18.25	$18.20
7 purchase totals =	$445.94		$492.2681	$492.27	$492.25	$492.20