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	$36.87	12.406%	$41.4441	$41.44	$41.45	$41.40
Purchase #2	$90.36	4.340%	$94.2816	$94.28	$94.30	$94.30
Purchase #3	$156.53	10.621%	$173.1551	$173.16	$173.15	$173.20
Purchase #4	$61.32	8.654%	$66.6266	$66.63	$66.65	$66.60
Purchase #5	$133.73	4.273%	$139.4443	$139.44	$139.45	$139.40
Purchase #6	$55.60	10.596%	$61.4914	$61.49	$61.50	$61.50
Purchase #7	$22.70	10.303%	$25.0388	$25.04	$25.05	$25.00
7 purchase totals =	$557.11		$601.4819	$601.48	$601.55	$601.40