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	$133.51	6.664%	$142.4071	$142.41	$142.40	$142.40
Purchase #2	$84.40	9.729%	$92.6113	$92.61	$92.60	$92.60
Purchase #3	$73.77	12.172%	$82.7493	$82.75	$82.75	$82.70
Purchase #4	$9.59	10.640%	$10.6104	$10.61	$10.60	$10.60
Purchase #5	$227.31	10.802%	$251.864	$251.86	$251.85	$251.90
Purchase #6	$53.27	4.667%	$55.7561	$55.76	$55.75	$55.80
Purchase #7	$41.47	5.333%	$43.6816	$43.68	$43.70	$43.70
7 purchase totals =	$623.32		$679.6798	$679.68	$679.65	$679.70