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	$83.75	3.188%	$86.42	$86.42	$86.40	$86.40
Purchase #2	$126.34	12.217%	$141.775	$141.78	$141.80	$141.80
Purchase #3	$200.45	5.687%	$211.8496	$211.85	$211.85	$211.80
Purchase #4	$144.57	13.748%	$164.4455	$164.45	$164.45	$164.40
Purchase #5	$174.39	6.368%	$185.4952	$185.50	$185.50	$185.50
Purchase #6	$92.65	11.305%	$103.1241	$103.12	$103.10	$103.10
Purchase #7	$79.90	12.597%	$89.965	$89.97	$89.95	$90.00
7 purchase totals =	$902.05		$983.0744	$983.09	$983.05	$983.00