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	$238.69	10.195%	$263.0244	$263.02	$263.00	$263.00
Purchase #2	$90.72	10.653%	$100.3844	$100.38	$100.40	$100.40
Purchase #3	$233.57	10.551%	$258.214	$258.21	$258.20	$258.20
Purchase #4	$171.84	9.782%	$188.6494	$188.65	$188.65	$188.60
Purchase #5	$108.33	8.848%	$117.915	$117.92	$117.90	$117.90
Purchase #6	$48.77	3.870%	$50.6574	$50.66	$50.65	$50.70
Purchase #7	$113.57	11.280%	$126.3807	$126.38	$126.40	$126.40
7 purchase totals =	$1,005.49		$1,105.2253	$1,105.22	$1,105.20	$1,105.20