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	$165.59	4.393%	$172.8644	$172.86	$172.85	$172.90
Purchase #2	$22.62	8.181%	$24.4705	$24.47	$24.45	$24.50
Purchase #3	$206.53	11.770%	$230.8386	$230.84	$230.85	$230.80
Purchase #4	$45.94	6.513%	$48.9321	$48.93	$48.95	$48.90
Purchase #5	$156.60	7.315%	$168.0553	$168.06	$168.05	$168.10
Purchase #6	$162.62	12.699%	$183.2711	$183.27	$183.25	$183.30
Purchase #7	$206.95	7.372%	$222.2064	$222.21	$222.20	$222.20
7 purchase totals =	$966.85		$1,050.6384	$1,050.64	$1,050.60	$1,050.70