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	$232.75	12.677%	$262.2557	$262.26	$262.25	$262.30
Purchase #2	$43.57	11.798%	$48.7104	$48.71	$48.70	$48.70
Purchase #3	$155.68	5.541%	$164.3062	$164.31	$164.30	$164.30
Purchase #4	$247.71	6.870%	$264.7277	$264.73	$264.75	$264.70
Purchase #5	$148.41	3.236%	$153.2125	$153.21	$153.20	$153.20
Purchase #6	$134.40	3.860%	$139.5878	$139.59	$139.60	$139.60
Purchase #7	$65.66	11.119%	$72.9607	$72.96	$72.95	$73.00
7 purchase totals =	$1,028.18		$1,105.7610	$1,105.77	$1,105.75	$1,105.80