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	$68.43	5.245%	$72.0192	$72.02	$72.00	$72.00
Purchase #2	$19.65	11.670%	$21.9432	$21.94	$21.95	$21.90
Purchase #3	$233.53	11.803%	$261.0935	$261.09	$261.10	$261.10
Purchase #4	$235.74	9.569%	$258.298	$258.30	$258.30	$258.30
Purchase #5	$40.52	11.824%	$45.3111	$45.31	$45.30	$45.30
Purchase #6	$214.25	5.279%	$225.5603	$225.56	$225.55	$225.60
Purchase #7	$14.78	4.305%	$15.4163	$15.42	$15.40	$15.40
7 purchase totals =	$826.90		$899.6416	$899.64	$899.60	$899.60