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	$59.32	13.130%	$67.1087	$67.11	$67.10	$67.10
Purchase #2	$208.61	9.337%	$228.0879	$228.09	$228.10	$228.10
Purchase #3	$94.76	8.282%	$102.608	$102.61	$102.60	$102.60
Purchase #4	$176.81	4.298%	$184.4093	$184.41	$184.40	$184.40
Purchase #5	$68.58	13.735%	$77.9995	$78.00	$78.00	$78.00
Purchase #6	$77.56	10.517%	$85.717	$85.72	$85.70	$85.70
Purchase #7	$180.94	5.126%	$190.215	$190.22	$190.20	$190.20
7 purchase totals =	$866.58		$936.1454	$936.16	$936.10	$936.10