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	$94.73	11.235%	$105.3729	$105.37	$105.35	$105.40
Purchase #2	$44.99	12.746%	$50.7244	$50.72	$50.70	$50.70
Purchase #3	$117.45	9.598%	$128.7229	$128.72	$128.70	$128.70
Purchase #4	$139.86	4.239%	$145.7887	$145.79	$145.80	$145.80
Purchase #5	$244.32	12.660%	$275.2509	$275.25	$275.25	$275.30
Purchase #6	$28.89	7.579%	$31.0796	$31.08	$31.10	$31.10
Purchase #7	$20.54	3.608%	$21.2811	$21.28	$21.30	$21.30
7 purchase totals =	$690.78		$758.2205	$758.21	$758.20	$758.30