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	$242.87	8.866%	$264.4029	$264.40	$264.40	$264.40
Purchase #2	$125.95	10.455%	$139.1181	$139.12	$139.10	$139.10
Purchase #3	$18.98	6.166%	$20.1503	$20.15	$20.15	$20.20
Purchase #4	$233.35	3.354%	$241.1766	$241.18	$241.20	$241.20
Purchase #5	$39.79	6.295%	$42.2948	$42.29	$42.30	$42.30
Purchase #6	$168.92	5.622%	$178.4167	$178.42	$178.40	$178.40
Purchase #7	$130.85	10.419%	$144.4833	$144.48	$144.50	$144.50
7 purchase totals =	$960.71		$1,030.0427	$1,030.04	$1,030.05	$1,030.10