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	$173.52	9.260%	$189.588	$189.59	$189.60	$189.60
Purchase #2	$94.25	6.216%	$100.1086	$100.11	$100.10	$100.10
Purchase #3	$90.62	7.138%	$97.0885	$97.09	$97.10	$97.10
Purchase #4	$48.34	4.102%	$50.3229	$50.32	$50.30	$50.30
Purchase #5	$53.60	13.575%	$60.8762	$60.88	$60.90	$60.90
Purchase #6	$58.72	13.811%	$66.8298	$66.83	$66.85	$66.80
Purchase #7	$16.90	3.472%	$17.4868	$17.49	$17.50	$17.50
7 purchase totals =	$535.95		$582.3008	$582.31	$582.35	$582.30