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	$111.44	10.504%	$123.1457	$123.15	$123.15	$123.10
Purchase #2	$119.97	11.135%	$133.3287	$133.33	$133.35	$133.30
Purchase #3	$250.45	10.358%	$276.3916	$276.39	$276.40	$276.40
Purchase #4	$147.25	6.428%	$156.7152	$156.72	$156.70	$156.70
Purchase #5	$32.33	4.583%	$33.8117	$33.81	$33.80	$33.80
Purchase #6	$112.67	10.172%	$124.1308	$124.13	$124.15	$124.10
Purchase #7	$92.60	12.799%	$104.4519	$104.45	$104.45	$104.50
7 purchase totals =	$866.71		$951.9756	$951.98	$952.00	$951.90