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	$101.72	10.509%	$112.4098	$112.41	$112.40	$112.40
Purchase #2	$160.60	4.709%	$168.1627	$168.16	$168.15	$168.20
Purchase #3	$20.33	12.417%	$22.8544	$22.85	$22.85	$22.90
Purchase #4	$147.36	3.160%	$152.0166	$152.02	$152.00	$152.00
Purchase #5	$83.25	6.745%	$88.8652	$88.87	$88.85	$88.90
Purchase #6	$173.71	13.379%	$196.9507	$196.95	$196.95	$197.00
Purchase #7	$28.94	13.353%	$32.8044	$32.80	$32.80	$32.80
7 purchase totals =	$715.91		$774.0638	$774.06	$774.00	$774.20