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	$245.77	4.160%	$255.994	$255.99	$256.00	$256.00
Purchase #2	$51.54	6.865%	$55.0782	$55.08	$55.10	$55.10
Purchase #3	$241.92	12.781%	$272.8398	$272.84	$272.85	$272.80
Purchase #4	$80.75	9.487%	$88.4108	$88.41	$88.40	$88.40
Purchase #5	$175.95	7.167%	$188.5603	$188.56	$188.55	$188.60
Purchase #6	$83.38	7.833%	$89.9112	$89.91	$89.90	$89.90
Purchase #7	$54.40	6.705%	$58.0475	$58.05	$58.05	$58.00
7 purchase totals =	$933.71		$1,008.8418	$1,008.84	$1,008.85	$1,008.80