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	$38.55	8.824%	$41.9517	$41.95	$41.95	$42.00
Purchase #2	$19.98	5.812%	$21.1412	$21.14	$21.15	$21.10
Purchase #3	$12.54	13.590%	$14.2442	$14.24	$14.25	$14.20
Purchase #4	$93.69	12.486%	$105.3881	$105.39	$105.40	$105.40
Purchase #5	$84.36	3.174%	$87.0376	$87.04	$87.05	$87.00
Purchase #6	$166.63	11.550%	$185.8758	$185.88	$185.90	$185.90
Purchase #7	$208.35	11.123%	$231.5248	$231.52	$231.50	$231.50
7 purchase totals =	$624.10		$687.1634	$687.16	$687.20	$687.10