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	$169.98	12.388%	$191.0371	$191.04	$191.05	$191.00
Purchase #2	$10.82	12.537%	$12.1765	$12.18	$12.20	$12.20
Purchase #3	$153.36	8.688%	$166.6839	$166.68	$166.70	$166.70
Purchase #4	$77.89	6.476%	$82.9342	$82.93	$82.95	$82.90
Purchase #5	$196.26	4.596%	$205.2801	$205.28	$205.30	$205.30
Purchase #6	$175.70	9.160%	$191.7941	$191.79	$191.80	$191.80
Purchase #7	$118.32	4.680%	$123.8574	$123.86	$123.85	$123.90
7 purchase totals =	$902.33		$973.7633	$973.76	$973.85	$973.80