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	$212.56	12.380%	$238.8749	$238.87	$238.85	$238.90
Purchase #2	$66.86	5.492%	$70.532	$70.53	$70.55	$70.50
Purchase #3	$153.99	13.671%	$175.042	$175.04	$175.05	$175.00
Purchase #4	$94.42	5.846%	$99.9398	$99.94	$99.95	$99.90
Purchase #5	$39.75	5.805%	$42.0575	$42.06	$42.05	$42.10
Purchase #6	$44.72	12.783%	$50.4366	$50.44	$50.45	$50.40
Purchase #7	$99.86	8.444%	$108.2922	$108.29	$108.30	$108.30
7 purchase totals =	$712.16		$785.1750	$785.17	$785.20	$785.10