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	$107.74	8.545%	$116.9464	$116.95	$116.95	$116.90
Purchase #2	$116.64	12.329%	$131.0205	$131.02	$131.00	$131.00
Purchase #3	$127.78	13.697%	$145.282	$145.28	$145.30	$145.30
Purchase #4	$165.70	13.292%	$187.7248	$187.72	$187.70	$187.70
Purchase #5	$199.31	7.152%	$213.5647	$213.56	$213.55	$213.60
Purchase #6	$32.77	7.381%	$35.1888	$35.19	$35.20	$35.20
Purchase #7	$30.32	11.789%	$33.8944	$33.89	$33.90	$33.90
7 purchase totals =	$780.26		$863.6216	$863.61	$863.60	$863.60