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	$183.28	9.461%	$200.6201	$200.62	$200.60	$200.60
Purchase #2	$196.94	4.492%	$205.7865	$205.79	$205.80	$205.80
Purchase #3	$44.69	3.807%	$46.3913	$46.39	$46.40	$46.40
Purchase #4	$79.71	7.748%	$85.8859	$85.89	$85.90	$85.90
Purchase #5	$154.67	8.741%	$168.1897	$168.19	$168.20	$168.20
Purchase #6	$137.46	9.714%	$150.8129	$150.81	$150.80	$150.80
Purchase #7	$76.32	5.467%	$80.4924	$80.49	$80.50	$80.50
7 purchase totals =	$873.07		$938.1788	$938.18	$938.20	$938.20