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	$145.79	12.679%	$164.2747	$164.27	$164.25	$164.30
Purchase #2	$238.69	7.239%	$255.9688	$255.97	$255.95	$256.00
Purchase #3	$132.78	7.482%	$142.7146	$142.71	$142.70	$142.70
Purchase #4	$248.72	6.149%	$264.0138	$264.01	$264.00	$264.00
Purchase #5	$118.41	11.194%	$131.6648	$131.66	$131.65	$131.70
Purchase #6	$129.77	5.480%	$136.8814	$136.88	$136.90	$136.90
Purchase #7	$161.29	3.120%	$166.3222	$166.32	$166.30	$166.30
7 purchase totals =	$1,175.45		$1,261.8403	$1,261.82	$1,261.75	$1,261.90