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	$97.47	8.189%	$105.4518	$105.45	$105.45	$105.50
Purchase #2	$32.45	4.426%	$33.8862	$33.89	$33.90	$33.90
Purchase #3	$183.92	13.111%	$208.0338	$208.03	$208.05	$208.00
Purchase #4	$229.78	13.123%	$259.934	$259.93	$259.95	$259.90
Purchase #5	$195.87	6.846%	$209.2793	$209.28	$209.30	$209.30
Purchase #6	$96.74	8.110%	$104.5856	$104.59	$104.60	$104.60
Purchase #7	$63.52	6.431%	$67.605	$67.61	$67.60	$67.60
7 purchase totals =	$899.75		$988.7757	$988.78	$988.85	$988.80