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	$153.67	6.638%	$163.8706	$163.87	$163.85	$163.90
Purchase #2	$43.64	3.468%	$45.1534	$45.15	$45.15	$45.20
Purchase #3	$85.74	12.587%	$96.5321	$96.53	$96.55	$96.50
Purchase #4	$82.59	8.194%	$89.3574	$89.36	$89.35	$89.40
Purchase #5	$106.84	10.653%	$118.2217	$118.22	$118.20	$118.20
Purchase #6	$144.81	12.195%	$162.4696	$162.47	$162.45	$162.50
Purchase #7	$10.35	7.757%	$11.1528	$11.15	$11.15	$11.20
7 purchase totals =	$627.64		$686.7576	$686.75	$686.70	$686.90