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	$244.75	8.110%	$264.5992	$264.60	$264.60	$264.60
Purchase #2	$79.28	13.653%	$90.1041	$90.10	$90.10	$90.10
Purchase #3	$147.73	4.172%	$153.8933	$153.89	$153.90	$153.90
Purchase #4	$130.58	9.352%	$142.7918	$142.79	$142.80	$142.80
Purchase #5	$229.90	13.459%	$260.8422	$260.84	$260.85	$260.80
Purchase #6	$105.45	10.424%	$116.4421	$116.44	$116.45	$116.40
Purchase #7	$241.71	6.443%	$257.2834	$257.28	$257.30	$257.30
7 purchase totals =	$1,179.40		$1,285.9561	$1,285.94	$1,286.00	$1,285.90