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	$42.79	5.713%	$45.2346	$45.23	$45.25	$45.20
Purchase #2	$26.26	4.636%	$27.4774	$27.48	$27.50	$27.50
Purchase #3	$156.94	5.489%	$165.5544	$165.55	$165.55	$165.60
Purchase #4	$241.46	12.677%	$272.0699	$272.07	$272.05	$272.10
Purchase #5	$143.97	6.176%	$152.8616	$152.86	$152.85	$152.90
Purchase #6	$224.41	4.859%	$235.3141	$235.31	$235.30	$235.30
Purchase #7	$158.72	3.691%	$164.5784	$164.58	$164.60	$164.60
7 purchase totals =	$994.55		$1,063.0904	$1,063.08	$1,063.10	$1,063.20