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	$85.88	13.123%	$97.15	$97.15	$97.15	$97.20
Purchase #2	$214.37	4.767%	$224.589	$224.59	$224.60	$224.60
Purchase #3	$158.65	5.569%	$167.4852	$167.49	$167.50	$167.50
Purchase #4	$153.36	8.296%	$166.0827	$166.08	$166.10	$166.10
Purchase #5	$106.35	11.507%	$118.5877	$118.59	$118.60	$118.60
Purchase #6	$215.48	5.781%	$227.9369	$227.94	$227.95	$227.90
Purchase #7	$136.46	4.680%	$142.8463	$142.85	$142.85	$142.80
7 purchase totals =	$1,070.55		$1,144.6778	$1,144.69	$1,144.75	$1,144.70