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	$226.92	3.762%	$235.4567	$235.46	$235.45	$235.50
Purchase #2	$153.25	9.726%	$168.1551	$168.16	$168.15	$168.20
Purchase #3	$65.97	6.611%	$70.3313	$70.33	$70.35	$70.30
Purchase #4	$245.56	10.501%	$271.3463	$271.35	$271.35	$271.30
Purchase #5	$36.60	6.237%	$38.8827	$38.88	$38.90	$38.90
Purchase #6	$100.51	11.719%	$112.2888	$112.29	$112.30	$112.30
Purchase #7	$30.72	4.219%	$32.0161	$32.02	$32.00	$32.00
7 purchase totals =	$859.53		$928.4770	$928.49	$928.50	$928.50