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	$130.60	11.823%	$146.0408	$146.04	$146.05	$146.00
Purchase #2	$112.32	5.441%	$118.4313	$118.43	$118.45	$118.40
Purchase #3	$189.63	3.479%	$196.2272	$196.23	$196.25	$196.20
Purchase #4	$13.71	6.500%	$14.6012	$14.60	$14.60	$14.60
Purchase #5	$51.47	6.638%	$54.8866	$54.89	$54.90	$54.90
Purchase #6	$67.45	3.847%	$70.0448	$70.04	$70.05	$70.00
Purchase #7	$57.79	6.327%	$61.4464	$61.45	$61.45	$61.40
7 purchase totals =	$622.97		$661.6783	$661.68	$661.75	$661.50