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	$194.51	3.700%	$201.7069	$201.71	$201.70	$201.70
Purchase #2	$126.95	12.544%	$142.8746	$142.87	$142.85	$142.90
Purchase #3	$111.45	4.146%	$116.0707	$116.07	$116.05	$116.10
Purchase #4	$136.66	4.554%	$142.8835	$142.88	$142.90	$142.90
Purchase #5	$192.37	9.479%	$210.6048	$210.60	$210.60	$210.60
Purchase #6	$123.92	7.111%	$132.732	$132.73	$132.75	$132.70
Purchase #7	$151.78	4.674%	$158.8742	$158.87	$158.85	$158.90
7 purchase totals =	$1,037.64		$1,105.7467	$1,105.73	$1,105.70	$1,105.80