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	$219.69	8.180%	$237.6606	$237.66	$237.65	$237.70
Purchase #2	$98.29	4.245%	$102.4624	$102.46	$102.45	$102.50
Purchase #3	$92.48	13.421%	$104.8917	$104.89	$104.90	$104.90
Purchase #4	$173.83	7.629%	$187.0915	$187.09	$187.10	$187.10
Purchase #5	$123.60	12.691%	$139.2861	$139.29	$139.30	$139.30
Purchase #6	$99.30	13.271%	$112.4781	$112.48	$112.50	$112.50
Purchase #7	$13.58	12.623%	$15.2942	$15.29	$15.30	$15.30
7 purchase totals =	$820.77		$899.1646	$899.16	$899.20	$899.30