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	$216.73	3.277%	$223.8322	$223.83	$223.85	$223.80
Purchase #2	$112.72	4.643%	$117.9536	$117.95	$117.95	$118.00
Purchase #3	$72.78	7.499%	$78.2378	$78.24	$78.25	$78.20
Purchase #4	$170.45	8.232%	$184.4814	$184.48	$184.50	$184.50
Purchase #5	$49.35	4.344%	$51.4938	$51.49	$51.50	$51.50
Purchase #6	$62.77	11.280%	$69.8505	$69.85	$69.85	$69.90
Purchase #7	$180.76	5.384%	$190.4921	$190.49	$190.50	$190.50
7 purchase totals =	$865.56		$916.3414	$916.33	$916.40	$916.40