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	$177.89	11.519%	$198.3811	$198.38	$198.40	$198.40
Purchase #2	$231.31	11.269%	$257.3763	$257.38	$257.40	$257.40
Purchase #3	$183.79	6.713%	$196.1278	$196.13	$196.15	$196.10
Purchase #4	$32.41	10.752%	$35.8947	$35.89	$35.90	$35.90
Purchase #5	$111.98	8.232%	$121.1982	$121.20	$121.20	$121.20
Purchase #6	$78.52	13.762%	$89.3259	$89.33	$89.35	$89.30
Purchase #7	$173.40	3.733%	$179.873	$179.87	$179.85	$179.90
7 purchase totals =	$989.30		$1,078.1770	$1,078.18	$1,078.25	$1,078.20