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	$66.72	8.422%	$72.3392	$72.34	$72.35	$72.30
Purchase #2	$227.55	12.364%	$255.6843	$255.68	$255.70	$255.70
Purchase #3	$147.85	11.552%	$164.9296	$164.93	$164.95	$164.90
Purchase #4	$58.89	4.639%	$61.6219	$61.62	$61.60	$61.60
Purchase #5	$110.68	11.751%	$123.686	$123.69	$123.70	$123.70
Purchase #6	$141.25	8.771%	$153.639	$153.64	$153.65	$153.60
Purchase #7	$33.52	9.166%	$36.5924	$36.59	$36.60	$36.60
7 purchase totals =	$786.46		$868.4924	$868.49	$868.55	$868.40