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	$89.55	8.196%	$96.8895	$96.89	$96.90	$96.90
Purchase #2	$226.78	6.275%	$241.0104	$241.01	$241.00	$241.00
Purchase #3	$168.72	6.178%	$179.1435	$179.14	$179.15	$179.10
Purchase #4	$156.74	12.406%	$176.1852	$176.19	$176.20	$176.20
Purchase #5	$54.81	4.146%	$57.0824	$57.08	$57.10	$57.10
Purchase #6	$220.78	10.482%	$243.9222	$243.92	$243.90	$243.90
Purchase #7	$142.26	5.864%	$150.6021	$150.60	$150.60	$150.60
7 purchase totals =	$1,059.64		$1,144.8353	$1,144.83	$1,144.85	$1,144.80