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	$147.40	5.578%	$155.622	$155.62	$155.60	$155.60
Purchase #2	$55.43	13.505%	$62.9158	$62.92	$62.90	$62.90
Purchase #3	$202.73	6.283%	$215.4675	$215.47	$215.45	$215.50
Purchase #4	$39.59	11.863%	$44.2866	$44.29	$44.30	$44.30
Purchase #5	$99.81	4.130%	$103.9322	$103.93	$103.95	$103.90
Purchase #6	$117.40	5.328%	$123.6551	$123.66	$123.65	$123.70
Purchase #7	$88.83	6.301%	$94.4272	$94.43	$94.45	$94.40
7 purchase totals =	$751.19		$800.3064	$800.32	$800.30	$800.30