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	$24.37	4.760%	$25.53	$25.53	$25.55	$25.50
Purchase #2	$59.65	6.599%	$63.5863	$63.59	$63.60	$63.60
Purchase #3	$28.43	13.450%	$32.2538	$32.25	$32.25	$32.30
Purchase #4	$145.30	7.469%	$156.1525	$156.15	$156.15	$156.20
Purchase #5	$208.32	9.576%	$228.2687	$228.27	$228.25	$228.30
Purchase #6	$196.28	13.301%	$222.3872	$222.39	$222.40	$222.40
Purchase #7	$134.61	3.547%	$139.3846	$139.38	$139.40	$139.40
7 purchase totals =	$796.96		$867.5631	$867.56	$867.60	$867.70