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	$143.79	5.721%	$152.0162	$152.02	$152.00	$152.00
Purchase #2	$154.87	11.501%	$172.6816	$172.68	$172.70	$172.70
Purchase #3	$199.38	3.277%	$205.9137	$205.91	$205.90	$205.90
Purchase #4	$150.25	13.747%	$170.9049	$170.90	$170.90	$170.90
Purchase #5	$154.41	9.801%	$169.5437	$169.54	$169.55	$169.50
Purchase #6	$199.68	11.320%	$222.2838	$222.28	$222.30	$222.30
Purchase #7	$192.70	3.826%	$200.0727	$200.07	$200.05	$200.10
7 purchase totals =	$1,195.08		$1,293.4166	$1,293.40	$1,293.40	$1,293.40