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	$101.85	9.307%	$111.3292	$111.33	$111.35	$111.30
Purchase #2	$6.83	9.685%	$7.4915	$7.49	$7.50	$7.50
Purchase #3	$15.94	11.490%	$17.7715	$17.77	$17.75	$17.80
Purchase #4	$70.90	9.827%	$77.8673	$77.87	$77.85	$77.90
Purchase #5	$131.33	7.368%	$141.0064	$141.01	$141.00	$141.00
Purchase #6	$100.81	11.561%	$112.4646	$112.46	$112.45	$112.50
Purchase #7	$75.61	11.764%	$84.5048	$84.50	$84.50	$84.50
7 purchase totals =	$503.27		$552.4353	$552.43	$552.40	$552.50