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	$168.94	13.626%	$191.9598	$191.96	$191.95	$192.00
Purchase #2	$126.34	12.648%	$142.3195	$142.32	$142.30	$142.30
Purchase #3	$195.40	13.682%	$222.1346	$222.13	$222.15	$222.10
Purchase #4	$101.71	7.366%	$109.202	$109.20	$109.20	$109.20
Purchase #5	$51.74	3.259%	$53.4262	$53.43	$53.45	$53.40
Purchase #6	$24.50	8.205%	$26.5102	$26.51	$26.50	$26.50
Purchase #7	$238.52	8.533%	$258.8729	$258.87	$258.85	$258.90
7 purchase totals =	$907.15		$1,004.4252	$1,004.42	$1,004.40	$1,004.40