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	$56.37	11.192%	$62.6789	$62.68	$62.70	$62.70
Purchase #2	$43.45	12.646%	$48.9447	$48.94	$48.95	$48.90
Purchase #3	$206.83	6.435%	$220.1395	$220.14	$220.15	$220.10
Purchase #4	$209.95	5.671%	$221.8563	$221.86	$221.85	$221.90
Purchase #5	$134.82	11.569%	$150.4173	$150.42	$150.40	$150.40
Purchase #6	$68.54	11.502%	$76.4235	$76.42	$76.40	$76.40
Purchase #7	$81.82	4.408%	$85.4266	$85.43	$85.45	$85.40
7 purchase totals =	$801.78		$865.8868	$865.89	$865.90	$865.80