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	$215.87	13.696%	$245.4356	$245.44	$245.45	$245.40
Purchase #2	$118.61	7.354%	$127.3326	$127.33	$127.35	$127.30
Purchase #3	$34.79	10.121%	$38.3111	$38.31	$38.30	$38.30
Purchase #4	$42.51	4.239%	$44.312	$44.31	$44.30	$44.30
Purchase #5	$126.38	4.780%	$132.421	$132.42	$132.40	$132.40
Purchase #6	$243.48	6.559%	$259.4499	$259.45	$259.45	$259.40
Purchase #7	$166.52	4.248%	$173.5938	$173.59	$173.60	$173.60
7 purchase totals =	$948.16		$1,020.8560	$1,020.85	$1,020.85	$1,020.70