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	$103.32	8.173%	$111.7643	$111.76	$111.75	$111.80
Purchase #2	$59.72	3.397%	$61.7487	$61.75	$61.75	$61.70
Purchase #3	$187.81	5.163%	$197.5066	$197.51	$197.50	$197.50
Purchase #4	$190.78	10.604%	$211.0103	$211.01	$211.00	$211.00
Purchase #5	$35.95	7.297%	$38.5733	$38.57	$38.55	$38.60
Purchase #6	$206.56	4.645%	$216.1547	$216.15	$216.15	$216.20
Purchase #7	$126.61	5.143%	$133.1216	$133.12	$133.10	$133.10
7 purchase totals =	$910.75		$969.8795	$969.87	$969.80	$969.90