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	$59.85	9.192%	$65.3514	$65.35	$65.35	$65.40
Purchase #2	$231.68	8.291%	$250.8886	$250.89	$250.90	$250.90
Purchase #3	$68.60	4.117%	$71.4243	$71.42	$71.40	$71.40
Purchase #4	$161.59	6.510%	$172.1095	$172.11	$172.10	$172.10
Purchase #5	$101.27	10.410%	$111.8122	$111.81	$111.80	$111.80
Purchase #6	$51.77	10.291%	$57.0977	$57.10	$57.10	$57.10
Purchase #7	$171.50	7.165%	$183.788	$183.79	$183.80	$183.80
7 purchase totals =	$846.26		$912.4717	$912.47	$912.45	$912.50