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	$144.27	11.801%	$161.2953	$161.30	$161.30	$161.30
Purchase #2	$193.90	3.145%	$199.9982	$200.00	$200.00	$200.00
Purchase #3	$67.51	4.455%	$70.5176	$70.52	$70.50	$70.50
Purchase #4	$149.86	8.702%	$162.9008	$162.90	$162.90	$162.90
Purchase #5	$93.32	11.158%	$103.7326	$103.73	$103.75	$103.70
Purchase #6	$131.37	4.522%	$137.3106	$137.31	$137.30	$137.30
Purchase #7	$214.78	10.402%	$237.1214	$237.12	$237.10	$237.10
7 purchase totals =	$995.01		$1,072.8765	$1,072.88	$1,072.85	$1,072.80