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	$149.69	5.785%	$158.3496	$158.35	$158.35	$158.30
Purchase #2	$125.77	9.863%	$138.1747	$138.17	$138.15	$138.20
Purchase #3	$88.44	13.278%	$100.1831	$100.18	$100.20	$100.20
Purchase #4	$148.66	10.872%	$164.8223	$164.82	$164.80	$164.80
Purchase #5	$88.28	12.157%	$99.0122	$99.01	$99.00	$99.00
Purchase #6	$214.39	9.109%	$233.9188	$233.92	$233.90	$233.90
Purchase #7	$44.35	12.685%	$49.9758	$49.98	$50.00	$50.00
7 purchase totals =	$859.58		$944.4365	$944.43	$944.40	$944.40