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	$98.41	6.805%	$105.1068	$105.11	$105.10	$105.10
Purchase #2	$111.47	6.679%	$118.9151	$118.92	$118.90	$118.90
Purchase #3	$234.59	11.730%	$262.1074	$262.11	$262.10	$262.10
Purchase #4	$58.53	5.141%	$61.539	$61.54	$61.55	$61.50
Purchase #5	$31.58	4.705%	$33.0658	$33.07	$33.05	$33.10
Purchase #6	$45.66	7.398%	$49.0379	$49.04	$49.05	$49.00
Purchase #7	$217.70	10.172%	$239.8444	$239.84	$239.85	$239.80
7 purchase totals =	$797.94		$869.6164	$869.63	$869.60	$869.50