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	$84.52	4.845%	$88.615	$88.62	$88.60	$88.60
Purchase #2	$99.69	3.822%	$103.5002	$103.50	$103.50	$103.50
Purchase #3	$78.65	11.120%	$87.3959	$87.40	$87.40	$87.40
Purchase #4	$132.54	11.380%	$147.6231	$147.62	$147.60	$147.60
Purchase #5	$59.63	3.195%	$61.5352	$61.54	$61.55	$61.50
Purchase #6	$138.93	3.567%	$143.8856	$143.89	$143.90	$143.90
Purchase #7	$237.74	11.406%	$264.8566	$264.86	$264.85	$264.90
7 purchase totals =	$831.70		$897.4116	$897.43	$897.40	$897.40