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	$145.32	4.167%	$151.3755	$151.38	$151.40	$151.40
Purchase #2	$92.71	7.506%	$99.6688	$99.67	$99.65	$99.70
Purchase #3	$165.42	4.603%	$173.0343	$173.03	$173.05	$173.00
Purchase #4	$160.39	4.566%	$167.7134	$167.71	$167.70	$167.70
Purchase #5	$245.51	11.849%	$274.6005	$274.60	$274.60	$274.60
Purchase #6	$79.33	3.483%	$82.0931	$82.09	$82.10	$82.10
Purchase #7	$172.99	8.440%	$187.5904	$187.59	$187.60	$187.60
7 purchase totals =	$1,061.67		$1,136.0760	$1,136.07	$1,136.10	$1,136.10