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	$95.41	5.427%	$100.5879	$100.59	$100.60	$100.60
Purchase #2	$205.42	8.240%	$222.3466	$222.35	$222.35	$222.30
Purchase #3	$113.90	5.209%	$119.8331	$119.83	$119.85	$119.80
Purchase #4	$117.83	12.417%	$132.461	$132.46	$132.45	$132.50
Purchase #5	$74.27	5.230%	$78.1543	$78.15	$78.15	$78.20
Purchase #6	$83.30	7.312%	$89.3909	$89.39	$89.40	$89.40
Purchase #7	$65.25	8.255%	$70.6364	$70.64	$70.65	$70.60
7 purchase totals =	$755.38		$813.4102	$813.41	$813.45	$813.40