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	$223.98	4.298%	$233.6067	$233.61	$233.60	$233.60
Purchase #2	$102.69	8.160%	$111.0695	$111.07	$111.05	$111.10
Purchase #3	$94.83	3.516%	$98.1642	$98.16	$98.15	$98.20
Purchase #4	$41.77	13.363%	$47.3517	$47.35	$47.35	$47.40
Purchase #5	$164.56	13.780%	$187.2364	$187.24	$187.25	$187.20
Purchase #6	$166.60	4.556%	$174.1903	$174.19	$174.20	$174.20
Purchase #7	$14.93	3.609%	$15.4688	$15.47	$15.45	$15.50
7 purchase totals =	$809.36		$867.0876	$867.09	$867.05	$867.20