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	$65.71	8.131%	$71.0529	$71.05	$71.05	$71.10
Purchase #2	$60.90	8.804%	$66.2616	$66.26	$66.25	$66.30
Purchase #3	$30.72	4.385%	$32.0671	$32.07	$32.05	$32.10
Purchase #4	$226.59	9.712%	$248.5964	$248.60	$248.60	$248.60
Purchase #5	$38.29	12.692%	$43.1498	$43.15	$43.15	$43.10
Purchase #6	$34.51	11.600%	$38.5132	$38.51	$38.50	$38.50
Purchase #7	$42.32	4.692%	$44.3057	$44.31	$44.30	$44.30
7 purchase totals =	$499.04		$543.9467	$543.95	$543.90	$544.00