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	$160.79	5.479%	$169.5997	$169.60	$169.60	$169.60
Purchase #2	$157.94	13.578%	$179.3851	$179.39	$179.40	$179.40
Purchase #3	$12.96	12.421%	$14.5698	$14.57	$14.55	$14.60
Purchase #4	$196.76	12.539%	$221.4317	$221.43	$221.45	$221.40
Purchase #5	$227.58	8.356%	$246.5966	$246.60	$246.60	$246.60
Purchase #6	$24.98	10.843%	$27.6886	$27.69	$27.70	$27.70
Purchase #7	$181.57	8.255%	$196.5586	$196.56	$196.55	$196.60
7 purchase totals =	$962.58		$1,055.8301	$1,055.84	$1,055.85	$1,055.90