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	$105.74	6.813%	$112.9441	$112.94	$112.95	$112.90
Purchase #2	$68.31	6.406%	$72.6859	$72.69	$72.70	$72.70
Purchase #3	$235.96	6.870%	$252.1705	$252.17	$252.15	$252.20
Purchase #4	$129.50	13.458%	$146.9281	$146.93	$146.95	$146.90
Purchase #5	$37.95	11.642%	$42.3681	$42.37	$42.35	$42.40
Purchase #6	$92.93	5.867%	$98.3822	$98.38	$98.40	$98.40
Purchase #7	$173.95	4.694%	$182.1152	$182.12	$182.10	$182.10
7 purchase totals =	$844.34		$907.5941	$907.60	$907.60	$907.60