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	$108.75	3.444%	$112.4954	$112.50	$112.50	$112.50
Purchase #2	$209.39	8.308%	$226.7861	$226.79	$226.80	$226.80
Purchase #3	$32.76	12.597%	$36.8868	$36.89	$36.90	$36.90
Purchase #4	$217.83	6.104%	$231.1263	$231.13	$231.15	$231.10
Purchase #5	$235.43	11.508%	$262.5233	$262.52	$262.50	$262.50
Purchase #6	$58.81	13.735%	$66.8876	$66.89	$66.90	$66.90
Purchase #7	$200.74	7.196%	$215.1853	$215.19	$215.20	$215.20
7 purchase totals =	$1,063.71		$1,151.8908	$1,151.91	$1,151.95	$1,151.90