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	$96.43	7.406%	$103.5716	$103.57	$103.55	$103.60
Purchase #2	$20.60	6.491%	$21.9371	$21.94	$21.95	$21.90
Purchase #3	$121.54	4.172%	$126.6106	$126.61	$126.60	$126.60
Purchase #4	$15.89	9.755%	$17.4401	$17.44	$17.45	$17.40
Purchase #5	$54.60	5.252%	$57.4676	$57.47	$57.45	$57.50
Purchase #6	$166.51	9.656%	$182.5882	$182.59	$182.60	$182.60
Purchase #7	$85.48	11.423%	$95.2444	$95.24	$95.25	$95.20
7 purchase totals =	$561.05		$604.8596	$604.86	$604.85	$604.80