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	$104.62	7.285%	$112.2416	$112.24	$112.25	$112.20
Purchase #2	$196.62	13.600%	$223.3603	$223.36	$223.35	$223.40
Purchase #3	$15.77	12.218%	$17.6968	$17.70	$17.70	$17.70
Purchase #4	$86.98	3.676%	$90.1774	$90.18	$90.20	$90.20
Purchase #5	$118.62	10.797%	$131.4274	$131.43	$131.45	$131.40
Purchase #6	$153.50	3.625%	$159.0644	$159.06	$159.05	$159.10
Purchase #7	$146.66	10.696%	$162.3468	$162.35	$162.35	$162.30
7 purchase totals =	$822.77		$896.3147	$896.32	$896.35	$896.30