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	$33.32	7.811%	$35.9226	$35.92	$35.90	$35.90
Purchase #2	$87.36	13.210%	$98.9003	$98.90	$98.90	$98.90
Purchase #3	$27.98	6.633%	$29.8359	$29.84	$29.85	$29.80
Purchase #4	$79.89	8.509%	$86.6878	$86.69	$86.70	$86.70
Purchase #5	$76.50	7.281%	$82.07	$82.07	$82.05	$82.10
Purchase #6	$141.29	7.151%	$151.3936	$151.39	$151.40	$151.40
Purchase #7	$35.70	10.614%	$39.4892	$39.49	$39.50	$39.50
7 purchase totals =	$482.04		$524.2994	$524.30	$524.30	$524.30