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	$87.78	13.719%	$99.8225	$99.82	$99.80	$99.80
Purchase #2	$143.25	13.139%	$162.0716	$162.07	$162.05	$162.10
Purchase #3	$145.44	10.649%	$160.9279	$160.93	$160.95	$160.90
Purchase #4	$58.99	3.532%	$61.0735	$61.07	$61.05	$61.10
Purchase #5	$137.64	9.817%	$151.1521	$151.15	$151.15	$151.20
Purchase #6	$111.80	10.139%	$123.1354	$123.14	$123.15	$123.10
Purchase #7	$91.57	4.776%	$95.9434	$95.94	$95.95	$95.90
7 purchase totals =	$776.47		$854.1264	$854.12	$854.10	$854.10