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	$43.74	6.122%	$46.4178	$46.42	$46.40	$46.40
Purchase #2	$197.72	5.488%	$208.5709	$208.57	$208.55	$208.60
Purchase #3	$153.27	12.765%	$172.8349	$172.83	$172.85	$172.80
Purchase #4	$213.42	11.820%	$238.6462	$238.65	$238.65	$238.60
Purchase #5	$104.85	6.430%	$111.5919	$111.59	$111.60	$111.60
Purchase #6	$20.95	8.132%	$22.6537	$22.65	$22.65	$22.70
Purchase #7	$74.72	10.639%	$82.6695	$82.67	$82.65	$82.70
7 purchase totals =	$808.67		$883.3849	$883.38	$883.35	$883.40