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	$51.80	5.355%	$54.5739	$54.57	$54.55	$54.60
Purchase #2	$140.86	5.526%	$148.6439	$148.64	$148.65	$148.60
Purchase #3	$47.83	10.499%	$52.8517	$52.85	$52.85	$52.90
Purchase #4	$204.69	4.671%	$214.2511	$214.25	$214.25	$214.30
Purchase #5	$237.34	5.467%	$250.3154	$250.32	$250.30	$250.30
Purchase #6	$152.73	6.236%	$162.2542	$162.25	$162.25	$162.30
Purchase #7	$154.94	11.336%	$172.504	$172.50	$172.50	$172.50
7 purchase totals =	$990.19		$1,055.3942	$1,055.38	$1,055.35	$1,055.50