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	$64.49	12.419%	$72.499	$72.50	$72.50	$72.50
Purchase #2	$22.83	12.338%	$25.6468	$25.65	$25.65	$25.60
Purchase #3	$208.60	12.761%	$235.2194	$235.22	$235.20	$235.20
Purchase #4	$25.78	6.577%	$27.4756	$27.48	$27.50	$27.50
Purchase #5	$234.92	8.783%	$255.553	$255.55	$255.55	$255.60
Purchase #6	$127.87	12.668%	$144.0686	$144.07	$144.05	$144.10
Purchase #7	$154.31	5.158%	$162.2693	$162.27	$162.25	$162.30
7 purchase totals =	$838.80		$922.7317	$922.74	$922.70	$922.80