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	$154.69	9.828%	$169.8929	$169.89	$169.90	$169.90
Purchase #2	$19.79	13.211%	$22.4045	$22.40	$22.40	$22.40
Purchase #3	$85.34	7.262%	$91.5374	$91.54	$91.55	$91.50
Purchase #4	$19.56	5.509%	$20.6376	$20.64	$20.65	$20.60
Purchase #5	$117.56	11.345%	$130.8972	$130.90	$130.90	$130.90
Purchase #6	$150.30	6.785%	$160.4979	$160.50	$160.50	$160.50
Purchase #7	$31.92	10.274%	$35.1995	$35.20	$35.20	$35.20
7 purchase totals =	$579.16		$631.0670	$631.07	$631.10	$631.00