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	$233.86	3.514%	$242.0778	$242.08	$242.10	$242.10
Purchase #2	$55.77	11.645%	$62.2644	$62.26	$62.25	$62.30
Purchase #3	$36.39	3.834%	$37.7852	$37.79	$37.80	$37.80
Purchase #4	$220.85	7.827%	$238.1359	$238.14	$238.15	$238.10
Purchase #5	$99.52	12.374%	$111.8346	$111.83	$111.85	$111.80
Purchase #6	$211.60	5.785%	$223.8411	$223.84	$223.85	$223.80
Purchase #7	$50.47	5.185%	$53.0869	$53.09	$53.10	$53.10
7 purchase totals =	$908.46		$969.0259	$969.03	$969.10	$969.00