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	$153.85	6.699%	$164.1564	$164.16	$164.15	$164.20
Purchase #2	$56.48	5.795%	$59.753	$59.75	$59.75	$59.80
Purchase #3	$193.25	3.384%	$199.7896	$199.79	$199.80	$199.80
Purchase #4	$236.53	11.836%	$264.5257	$264.53	$264.55	$264.50
Purchase #5	$176.52	6.748%	$188.4316	$188.43	$188.45	$188.40
Purchase #6	$128.60	3.126%	$132.62	$132.62	$132.60	$132.60
Purchase #7	$181.25	9.700%	$198.8313	$198.83	$198.85	$198.80
7 purchase totals =	$1,126.48		$1,208.1076	$1,208.11	$1,208.15	$1,208.10