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	$158.60	10.717%	$175.5972	$175.60	$175.60	$175.60
Purchase #2	$240.75	11.422%	$268.2485	$268.25	$268.25	$268.20
Purchase #3	$143.64	10.329%	$158.4766	$158.48	$158.50	$158.50
Purchase #4	$70.32	11.184%	$78.1846	$78.18	$78.20	$78.20
Purchase #5	$54.77	9.328%	$59.8789	$59.88	$59.90	$59.90
Purchase #6	$8.65	13.405%	$9.8095	$9.81	$9.80	$9.80
Purchase #7	$112.61	11.615%	$125.6897	$125.69	$125.70	$125.70
7 purchase totals =	$789.34		$875.8850	$875.89	$875.95	$875.90