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	$218.56	7.857%	$235.7323	$235.73	$235.75	$235.70
Purchase #2	$123.93	3.197%	$127.892	$127.89	$127.90	$127.90
Purchase #3	$197.53	12.748%	$222.7111	$222.71	$222.70	$222.70
Purchase #4	$126.90	11.467%	$141.4516	$141.45	$141.45	$141.50
Purchase #5	$196.91	7.239%	$211.1643	$211.16	$211.15	$211.20
Purchase #6	$154.44	6.321%	$164.2022	$164.20	$164.20	$164.20
Purchase #7	$47.89	4.128%	$49.8669	$49.87	$49.85	$49.90
7 purchase totals =	$1,066.16		$1,153.0204	$1,153.01	$1,153.00	$1,153.10