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	$76.58	12.540%	$86.1831	$86.18	$86.20	$86.20
Purchase #2	$37.90	8.193%	$41.0051	$41.01	$41.00	$41.00
Purchase #3	$84.33	5.699%	$89.136	$89.14	$89.15	$89.10
Purchase #4	$21.82	11.394%	$24.3062	$24.31	$24.30	$24.30
Purchase #5	$190.76	12.840%	$215.2536	$215.25	$215.25	$215.30
Purchase #6	$134.90	6.283%	$143.3758	$143.38	$143.40	$143.40
Purchase #7	$153.52	7.570%	$165.1415	$165.14	$165.15	$165.10
7 purchase totals =	$699.81		$764.4013	$764.41	$764.45	$764.40