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	$38.95	13.158%	$44.075	$44.08	$44.10	$44.10
Purchase #2	$113.40	11.744%	$126.7177	$126.72	$126.70	$126.70
Purchase #3	$183.88	5.606%	$194.1883	$194.19	$194.20	$194.20
Purchase #4	$250.70	4.112%	$261.0088	$261.01	$261.00	$261.00
Purchase #5	$187.78	4.764%	$196.7258	$196.73	$196.75	$196.70
Purchase #6	$241.84	5.495%	$255.1291	$255.13	$255.15	$255.10
Purchase #7	$67.72	4.285%	$70.6218	$70.62	$70.60	$70.60
7 purchase totals =	$1,084.27		$1,148.4665	$1,148.48	$1,148.50	$1,148.40