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	$241.25	13.741%	$274.4002	$274.40	$274.40	$274.40
Purchase #2	$23.74	3.440%	$24.5567	$24.56	$24.55	$24.60
Purchase #3	$227.63	11.226%	$253.1837	$253.18	$253.20	$253.20
Purchase #4	$97.93	7.739%	$105.5088	$105.51	$105.50	$105.50
Purchase #5	$146.35	5.188%	$153.9426	$153.94	$153.95	$153.90
Purchase #6	$148.90	7.716%	$160.3891	$160.39	$160.40	$160.40
Purchase #7	$44.56	6.480%	$47.4475	$47.45	$47.45	$47.40
7 purchase totals =	$930.36		$1,019.4286	$1,019.43	$1,019.45	$1,019.40