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	$160.40	8.747%	$174.4302	$174.43	$174.45	$174.40
Purchase #2	$135.60	5.323%	$142.818	$142.82	$142.80	$142.80
Purchase #3	$153.42	13.378%	$173.9445	$173.94	$173.95	$173.90
Purchase #4	$181.50	11.794%	$202.9061	$202.91	$202.90	$202.90
Purchase #5	$30.61	7.613%	$32.9403	$32.94	$32.95	$32.90
Purchase #6	$28.42	13.843%	$32.3542	$32.35	$32.35	$32.40
Purchase #7	$131.50	4.829%	$137.8501	$137.85	$137.85	$137.90
7 purchase totals =	$821.45		$897.2434	$897.24	$897.25	$897.20