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	$190.64	4.780%	$199.7526	$199.75	$199.75	$199.80
Purchase #2	$151.29	12.867%	$170.7565	$170.76	$170.75	$170.80
Purchase #3	$71.92	9.733%	$78.92	$78.92	$78.90	$78.90
Purchase #4	$55.31	4.295%	$57.6856	$57.69	$57.70	$57.70
Purchase #5	$74.39	12.376%	$83.5965	$83.60	$83.60	$83.60
Purchase #6	$179.60	5.126%	$188.8063	$188.81	$188.80	$188.80
Purchase #7	$58.28	7.126%	$62.433	$62.43	$62.45	$62.40
7 purchase totals =	$781.43		$841.9505	$841.96	$841.95	$842.00