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	$143.96	6.477%	$153.2843	$153.28	$153.30	$153.30
Purchase #2	$50.31	8.739%	$54.7066	$54.71	$54.70	$54.70
Purchase #3	$51.71	3.577%	$53.5597	$53.56	$53.55	$53.60
Purchase #4	$204.91	5.430%	$216.0366	$216.04	$216.05	$216.00
Purchase #5	$224.26	6.434%	$238.6889	$238.69	$238.70	$238.70
Purchase #6	$31.39	13.311%	$35.5683	$35.57	$35.55	$35.60
Purchase #7	$151.64	13.769%	$172.5193	$172.52	$172.50	$172.50
7 purchase totals =	$858.18		$924.3637	$924.37	$924.35	$924.40