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	$211.42	5.118%	$222.2405	$222.24	$222.25	$222.20
Purchase #2	$52.43	13.712%	$59.6192	$59.62	$59.60	$59.60
Purchase #3	$239.37	11.103%	$265.9473	$265.95	$265.95	$265.90
Purchase #4	$38.54	5.557%	$40.6817	$40.68	$40.70	$40.70
Purchase #5	$83.67	4.337%	$87.2988	$87.30	$87.30	$87.30
Purchase #6	$6.77	5.477%	$7.1408	$7.14	$7.15	$7.10
Purchase #7	$29.42	6.399%	$31.3026	$31.30	$31.30	$31.30
7 purchase totals =	$661.62		$714.2309	$714.23	$714.25	$714.10