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	$45.60	8.565%	$49.5056	$49.51	$49.50	$49.50
Purchase #2	$49.40	13.418%	$56.0285	$56.03	$56.05	$56.00
Purchase #3	$200.54	4.419%	$209.4019	$209.40	$209.40	$209.40
Purchase #4	$56.53	6.366%	$60.1287	$60.13	$60.15	$60.10
Purchase #5	$143.57	6.338%	$152.6695	$152.67	$152.65	$152.70
Purchase #6	$73.34	12.568%	$82.5574	$82.56	$82.55	$82.60
Purchase #7	$99.32	12.316%	$111.5523	$111.55	$111.55	$111.60
7 purchase totals =	$668.30		$721.8439	$721.85	$721.85	$721.90