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	$112.86	4.457%	$117.8902	$117.89	$117.90	$117.90
Purchase #2	$81.50	5.603%	$86.0664	$86.07	$86.05	$86.10
Purchase #3	$111.55	6.473%	$118.7706	$118.77	$118.75	$118.80
Purchase #4	$156.43	6.131%	$166.0207	$166.02	$166.00	$166.00
Purchase #5	$40.65	12.381%	$45.6829	$45.68	$45.70	$45.70
Purchase #6	$62.94	11.842%	$70.3934	$70.39	$70.40	$70.40
Purchase #7	$169.64	12.472%	$190.7975	$190.80	$190.80	$190.80
7 purchase totals =	$735.57		$795.6217	$795.62	$795.60	$795.70