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	$210.54	3.613%	$218.1468	$218.15	$218.15	$218.10
Purchase #2	$104.48	6.656%	$111.4342	$111.43	$111.45	$111.40
Purchase #3	$196.78	11.846%	$220.0906	$220.09	$220.10	$220.10
Purchase #4	$92.66	9.540%	$101.4998	$101.50	$101.50	$101.50
Purchase #5	$132.44	5.301%	$139.4606	$139.46	$139.45	$139.50
Purchase #6	$96.70	5.106%	$101.6375	$101.64	$101.65	$101.60
Purchase #7	$151.60	3.194%	$156.4421	$156.44	$156.45	$156.40
7 purchase totals =	$985.20		$1,048.7116	$1,048.71	$1,048.75	$1,048.60