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	$131.83	8.383%	$142.8813	$142.88	$142.90	$142.90
Purchase #2	$135.45	3.816%	$140.6188	$140.62	$140.60	$140.60
Purchase #3	$91.57	5.123%	$96.2611	$96.26	$96.25	$96.30
Purchase #4	$87.33	10.505%	$96.504	$96.50	$96.50	$96.50
Purchase #5	$137.83	11.790%	$154.0802	$154.08	$154.10	$154.10
Purchase #6	$173.29	13.434%	$196.5698	$196.57	$196.55	$196.60
Purchase #7	$44.66	5.461%	$47.0989	$47.10	$47.10	$47.10
7 purchase totals =	$801.96		$874.0141	$874.01	$874.00	$874.10