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	$114.90	11.276%	$127.8561	$127.86	$127.85	$127.90
Purchase #2	$164.54	6.602%	$175.4029	$175.40	$175.40	$175.40
Purchase #3	$82.58	6.742%	$88.1475	$88.15	$88.15	$88.10
Purchase #4	$12.99	12.766%	$14.6483	$14.65	$14.65	$14.60
Purchase #5	$208.28	9.799%	$228.6894	$228.69	$228.70	$228.70
Purchase #6	$65.27	7.491%	$70.1594	$70.16	$70.15	$70.20
Purchase #7	$135.92	11.539%	$151.6038	$151.60	$151.60	$151.60
7 purchase totals =	$784.48		$856.5074	$856.51	$856.50	$856.50