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	$242.50	9.490%	$265.5133	$265.51	$265.50	$265.50
Purchase #2	$122.70	13.558%	$139.3357	$139.34	$139.35	$139.30
Purchase #3	$162.62	5.857%	$172.1447	$172.14	$172.15	$172.10
Purchase #4	$166.88	7.323%	$179.1006	$179.10	$179.10	$179.10
Purchase #5	$205.40	11.759%	$229.553	$229.55	$229.55	$229.60
Purchase #6	$177.61	12.376%	$199.591	$199.59	$199.60	$199.60
Purchase #7	$243.71	6.842%	$260.3846	$260.38	$260.40	$260.40
7 purchase totals =	$1,321.42		$1,445.6229	$1,445.61	$1,445.65	$1,445.60