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	$187.91	10.793%	$208.1911	$208.19	$208.20	$208.20
Purchase #2	$223.46	13.756%	$254.1992	$254.20	$254.20	$254.20
Purchase #3	$199.98	11.274%	$222.5257	$222.53	$222.55	$222.50
Purchase #4	$173.47	5.604%	$183.1913	$183.19	$183.20	$183.20
Purchase #5	$16.83	10.624%	$18.618	$18.62	$18.60	$18.60
Purchase #6	$115.69	10.123%	$127.4013	$127.40	$127.40	$127.40
Purchase #7	$78.62	10.446%	$86.8326	$86.83	$86.85	$86.80
7 purchase totals =	$995.96		$1,100.9592	$1,100.96	$1,101.00	$1,100.90