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	$115.77	11.353%	$128.9134	$128.91	$128.90	$128.90
Purchase #2	$122.85	3.554%	$127.2161	$127.22	$127.20	$127.20
Purchase #3	$132.75	8.577%	$144.136	$144.14	$144.15	$144.10
Purchase #4	$38.38	5.443%	$40.469	$40.47	$40.45	$40.50
Purchase #5	$35.44	9.697%	$38.8766	$38.88	$38.90	$38.90
Purchase #6	$59.75	7.742%	$64.3758	$64.38	$64.40	$64.40
Purchase #7	$187.78	11.456%	$209.2921	$209.29	$209.30	$209.30
7 purchase totals =	$692.72		$753.2790	$753.29	$753.30	$753.30