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	$51.92	5.400%	$54.7237	$54.72	$54.70	$54.70
Purchase #2	$10.89	8.867%	$11.8556	$11.86	$11.85	$11.90
Purchase #3	$108.68	13.465%	$123.3138	$123.31	$123.30	$123.30
Purchase #4	$22.42	6.535%	$23.8851	$23.89	$23.90	$23.90
Purchase #5	$185.43	4.865%	$194.4512	$194.45	$194.45	$194.50
Purchase #6	$84.89	13.771%	$96.5802	$96.58	$96.60	$96.60
Purchase #7	$216.42	11.481%	$241.2672	$241.27	$241.25	$241.30
7 purchase totals =	$680.65		$746.0768	$746.08	$746.05	$746.20