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	$57.90	9.552%	$63.4306	$63.43	$63.45	$63.40
Purchase #2	$183.83	6.743%	$196.2257	$196.23	$196.25	$196.20
Purchase #3	$159.69	11.757%	$178.4648	$178.46	$178.45	$178.50
Purchase #4	$167.74	12.670%	$188.9927	$188.99	$189.00	$189.00
Purchase #5	$57.52	13.750%	$65.429	$65.43	$65.45	$65.40
Purchase #6	$64.55	11.318%	$71.8558	$71.86	$71.85	$71.90
Purchase #7	$196.30	5.765%	$207.6167	$207.62	$207.60	$207.60
7 purchase totals =	$887.53		$972.0153	$972.02	$972.05	$972.00