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	$157.90	6.142%	$167.5982	$167.60	$167.60	$167.60
Purchase #2	$78.59	8.549%	$85.3087	$85.31	$85.30	$85.30
Purchase #3	$57.60	8.700%	$62.6112	$62.61	$62.60	$62.60
Purchase #4	$59.70	10.454%	$65.941	$65.94	$65.95	$65.90
Purchase #5	$190.92	7.728%	$205.6743	$205.67	$205.65	$205.70
Purchase #6	$166.68	11.160%	$185.2815	$185.28	$185.30	$185.30
Purchase #7	$202.76	12.509%	$228.1232	$228.12	$228.10	$228.10
7 purchase totals =	$914.15		$1,000.5381	$1,000.53	$1,000.50	$1,000.50