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	$153.76	9.651%	$168.5994	$168.60	$168.60	$168.60
Purchase #2	$232.66	11.236%	$258.8017	$258.80	$258.80	$258.80
Purchase #3	$37.44	13.353%	$42.4394	$42.44	$42.45	$42.40
Purchase #4	$135.38	10.127%	$149.0899	$149.09	$149.10	$149.10
Purchase #5	$140.74	13.537%	$159.792	$159.79	$159.80	$159.80
Purchase #6	$145.89	4.651%	$152.6753	$152.68	$152.70	$152.70
Purchase #7	$79.81	12.840%	$90.0576	$90.06	$90.05	$90.10
7 purchase totals =	$925.68		$1,021.4553	$1,021.46	$1,021.50	$1,021.50