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	$73.97	3.422%	$76.5013	$76.50	$76.50	$76.50
Purchase #2	$9.86	12.530%	$11.0955	$11.10	$11.10	$11.10
Purchase #3	$210.64	11.248%	$234.3328	$234.33	$234.35	$234.30
Purchase #4	$104.33	4.862%	$109.4025	$109.40	$109.40	$109.40
Purchase #5	$236.65	3.298%	$244.4547	$244.45	$244.45	$244.50
Purchase #6	$44.89	3.623%	$46.5164	$46.52	$46.50	$46.50
Purchase #7	$100.57	8.211%	$108.8278	$108.83	$108.85	$108.80
7 purchase totals =	$780.91		$831.1310	$831.13	$831.15	$831.10