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	$228.50	5.846%	$241.8581	$241.86	$241.85	$241.90
Purchase #2	$126.65	3.655%	$131.2791	$131.28	$131.30	$131.30
Purchase #3	$116.63	9.551%	$127.7693	$127.77	$127.75	$127.80
Purchase #4	$234.69	12.309%	$263.578	$263.58	$263.60	$263.60
Purchase #5	$143.44	13.285%	$162.496	$162.50	$162.50	$162.50
Purchase #6	$18.83	11.778%	$21.0478	$21.05	$21.05	$21.00
Purchase #7	$57.66	8.363%	$62.4821	$62.48	$62.50	$62.50
7 purchase totals =	$926.40		$1,010.5104	$1,010.52	$1,010.55	$1,010.60