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	$157.63	4.310%	$164.4239	$164.42	$164.40	$164.40
Purchase #2	$211.54	4.127%	$220.2703	$220.27	$220.25	$220.30
Purchase #3	$56.53	13.217%	$64.0016	$64.00	$64.00	$64.00
Purchase #4	$130.94	5.568%	$138.2307	$138.23	$138.25	$138.20
Purchase #5	$111.60	11.613%	$124.5601	$124.56	$124.55	$124.60
Purchase #6	$88.66	13.537%	$100.6619	$100.66	$100.65	$100.70
Purchase #7	$231.42	10.288%	$255.2285	$255.23	$255.25	$255.20
7 purchase totals =	$988.32		$1,067.3770	$1,067.37	$1,067.35	$1,067.40