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	$33.46	13.380%	$37.9369	$37.94	$37.95	$37.90
Purchase #2	$145.61	8.864%	$158.5169	$158.52	$158.50	$158.50
Purchase #3	$231.25	10.404%	$255.3093	$255.31	$255.30	$255.30
Purchase #4	$79.60	3.603%	$82.468	$82.47	$82.45	$82.50
Purchase #5	$207.74	13.240%	$235.2448	$235.24	$235.25	$235.20
Purchase #6	$160.70	12.776%	$181.231	$181.23	$181.25	$181.20
Purchase #7	$143.52	12.661%	$161.6911	$161.69	$161.70	$161.70
7 purchase totals =	$1,001.88		$1,112.3980	$1,112.40	$1,112.40	$1,112.30