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	$125.27	13.733%	$142.4733	$142.47	$142.45	$142.50
Purchase #2	$124.95	4.744%	$130.8776	$130.88	$130.90	$130.90
Purchase #3	$34.91	4.247%	$36.3926	$36.39	$36.40	$36.40
Purchase #4	$79.64	7.245%	$85.4099	$85.41	$85.40	$85.40
Purchase #5	$133.40	6.610%	$142.2177	$142.22	$142.20	$142.20
Purchase #6	$53.47	5.157%	$56.2274	$56.23	$56.25	$56.20
Purchase #7	$18.56	12.131%	$20.8115	$20.81	$20.80	$20.80
7 purchase totals =	$570.20		$614.4100	$614.41	$614.40	$614.40