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	$214.56	3.212%	$221.4517	$221.45	$221.45	$221.50
Purchase #2	$189.56	12.658%	$213.5545	$213.55	$213.55	$213.60
Purchase #3	$72.50	11.245%	$80.6526	$80.65	$80.65	$80.70
Purchase #4	$116.47	4.543%	$121.7612	$121.76	$121.75	$121.80
Purchase #5	$248.52	11.526%	$277.1644	$277.16	$277.15	$277.20
Purchase #6	$249.30	5.671%	$263.4378	$263.44	$263.45	$263.40
Purchase #7	$40.40	11.528%	$45.0573	$45.06	$45.05	$45.10
7 purchase totals =	$1,131.31		$1,223.0795	$1,223.07	$1,223.05	$1,223.30