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	$79.59	13.128%	$90.0386	$90.04	$90.05	$90.00
Purchase #2	$56.86	5.696%	$60.0987	$60.10	$60.10	$60.10
Purchase #3	$150.32	5.360%	$158.3772	$158.38	$158.40	$158.40
Purchase #4	$136.84	11.345%	$152.3645	$152.36	$152.35	$152.40
Purchase #5	$215.29	12.130%	$241.4047	$241.40	$241.40	$241.40
Purchase #6	$197.59	5.369%	$208.1986	$208.20	$208.20	$208.20
Purchase #7	$102.36	10.266%	$112.8683	$112.87	$112.85	$112.90
7 purchase totals =	$938.85		$1,023.3506	$1,023.35	$1,023.35	$1,023.40