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	$105.43	3.808%	$109.4448	$109.44	$109.45	$109.40
Purchase #2	$140.34	8.111%	$151.723	$151.72	$151.70	$151.70
Purchase #3	$89.50	9.601%	$98.0929	$98.09	$98.10	$98.10
Purchase #4	$99.68	4.420%	$104.0859	$104.09	$104.10	$104.10
Purchase #5	$196.34	10.489%	$216.9341	$216.93	$216.95	$216.90
Purchase #6	$129.96	11.178%	$144.4869	$144.49	$144.50	$144.50
Purchase #7	$52.97	8.850%	$57.6578	$57.66	$57.65	$57.70
7 purchase totals =	$814.22		$882.4254	$882.42	$882.45	$882.40