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	$57.71	5.763%	$61.0358	$61.04	$61.05	$61.00
Purchase #2	$42.94	4.250%	$44.765	$44.77	$44.75	$44.80
Purchase #3	$237.58	10.597%	$262.7564	$262.76	$262.75	$262.80
Purchase #4	$181.85	10.190%	$200.3805	$200.38	$200.40	$200.40
Purchase #5	$153.66	11.822%	$171.8257	$171.83	$171.85	$171.80
Purchase #6	$169.36	4.108%	$176.3173	$176.32	$176.30	$176.30
Purchase #7	$108.52	7.399%	$116.5494	$116.55	$116.55	$116.50
7 purchase totals =	$951.62		$1,033.6301	$1,033.65	$1,033.65	$1,033.60