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	$64.96	4.450%	$67.8507	$67.85	$67.85	$67.90
Purchase #2	$90.75	13.429%	$102.9368	$102.94	$102.95	$102.90
Purchase #3	$233.32	13.511%	$264.8439	$264.84	$264.85	$264.80
Purchase #4	$146.97	11.677%	$164.1317	$164.13	$164.15	$164.10
Purchase #5	$27.47	3.294%	$28.3749	$28.37	$28.35	$28.40
Purchase #6	$101.58	10.546%	$112.2926	$112.29	$112.30	$112.30
Purchase #7	$167.47	3.747%	$173.7451	$173.75	$173.75	$173.70
7 purchase totals =	$832.52		$914.1757	$914.17	$914.20	$914.10