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	$241.88	10.220%	$266.6001	$266.60	$266.60	$266.60
Purchase #2	$56.34	9.742%	$61.8286	$61.83	$61.85	$61.80
Purchase #3	$154.83	10.669%	$171.3488	$171.35	$171.35	$171.30
Purchase #4	$79.73	13.855%	$90.7766	$90.78	$90.80	$90.80
Purchase #5	$206.89	6.792%	$220.942	$220.94	$220.95	$220.90
Purchase #6	$95.93	3.419%	$99.2098	$99.21	$99.20	$99.20
Purchase #7	$46.47	13.312%	$52.6561	$52.66	$52.65	$52.70
7 purchase totals =	$882.07		$963.3620	$963.37	$963.40	$963.30