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	$182.39	13.751%	$207.4704	$207.47	$207.45	$207.50
Purchase #2	$220.51	10.857%	$244.4508	$244.45	$244.45	$244.50
Purchase #3	$135.40	6.858%	$144.6857	$144.69	$144.70	$144.70
Purchase #4	$185.30	3.228%	$191.2815	$191.28	$191.30	$191.30
Purchase #5	$169.78	13.216%	$192.2181	$192.22	$192.20	$192.20
Purchase #6	$26.59	11.364%	$29.6117	$29.61	$29.60	$29.60
Purchase #7	$140.85	4.456%	$147.1263	$147.13	$147.15	$147.10
7 purchase totals =	$1,060.82		$1,156.8445	$1,156.85	$1,156.85	$1,156.90