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	$114.77	11.379%	$127.8297	$127.83	$127.85	$127.80
Purchase #2	$236.54	4.858%	$248.0311	$248.03	$248.05	$248.00
Purchase #3	$36.68	10.522%	$40.5395	$40.54	$40.55	$40.50
Purchase #4	$180.48	13.793%	$205.3736	$205.37	$205.35	$205.40
Purchase #5	$178.39	6.813%	$190.5437	$190.54	$190.55	$190.50
Purchase #6	$139.77	12.412%	$157.1183	$157.12	$157.10	$157.10
Purchase #7	$74.76	3.149%	$77.1142	$77.11	$77.10	$77.10
7 purchase totals =	$961.39		$1,046.5501	$1,046.54	$1,046.55	$1,046.40