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	$65.62	8.578%	$71.2489	$71.25	$71.25	$71.20
Purchase #2	$41.74	13.808%	$47.5035	$47.50	$47.50	$47.50
Purchase #3	$78.76	5.548%	$83.1296	$83.13	$83.15	$83.10
Purchase #4	$26.48	4.719%	$27.7296	$27.73	$27.75	$27.70
Purchase #5	$207.30	7.813%	$223.4963	$223.50	$223.50	$223.50
Purchase #6	$216.40	10.200%	$238.4728	$238.47	$238.45	$238.50
Purchase #7	$35.60	5.293%	$37.4843	$37.48	$37.50	$37.50
7 purchase totals =	$671.90		$729.0650	$729.06	$729.10	$729.00