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	$92.58	4.800%	$97.0238	$97.02	$97.00	$97.00
Purchase #2	$82.75	6.441%	$88.0799	$88.08	$88.10	$88.10
Purchase #3	$149.45	10.723%	$165.4755	$165.48	$165.50	$165.50
Purchase #4	$47.86	9.716%	$52.5101	$52.51	$52.50	$52.50
Purchase #5	$112.94	3.283%	$116.6478	$116.65	$116.65	$116.60
Purchase #6	$195.68	13.518%	$222.132	$222.13	$222.15	$222.10
Purchase #7	$35.45	6.417%	$37.7248	$37.72	$37.70	$37.70
7 purchase totals =	$716.71		$779.5939	$779.59	$779.60	$779.50