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	$46.92	13.698%	$53.3471	$53.35	$53.35	$53.30
Purchase #2	$127.51	9.366%	$139.4526	$139.45	$139.45	$139.50
Purchase #3	$16.28	13.411%	$18.4633	$18.46	$18.45	$18.50
Purchase #4	$160.70	5.539%	$169.6012	$169.60	$169.60	$169.60
Purchase #5	$85.54	12.663%	$96.3719	$96.37	$96.35	$96.40
Purchase #6	$17.72	13.431%	$20.1	$20.10	$20.10	$20.10
Purchase #7	$207.36	8.428%	$224.8363	$224.84	$224.85	$224.80
7 purchase totals =	$662.03		$722.1724	$722.17	$722.15	$722.20