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	$213.70	3.791%	$221.8014	$221.80	$221.80	$221.80
Purchase #2	$207.70	8.728%	$225.8281	$225.83	$225.85	$225.80
Purchase #3	$37.63	12.802%	$42.4474	$42.45	$42.45	$42.40
Purchase #4	$248.68	13.257%	$281.6475	$281.65	$281.65	$281.60
Purchase #5	$110.65	5.500%	$116.7358	$116.74	$116.75	$116.70
Purchase #6	$74.77	5.275%	$78.7141	$78.71	$78.70	$78.70
Purchase #7	$196.77	4.152%	$204.9399	$204.94	$204.95	$204.90
7 purchase totals =	$1,089.90		$1,172.1142	$1,172.12	$1,172.15	$1,171.90