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	$197.76	12.769%	$223.012	$223.01	$223.00	$223.00
Purchase #2	$105.32	9.632%	$115.4644	$115.46	$115.45	$115.50
Purchase #3	$15.94	7.830%	$17.1881	$17.19	$17.20	$17.20
Purchase #4	$198.94	10.319%	$219.4686	$219.47	$219.45	$219.50
Purchase #5	$29.29	11.687%	$32.7131	$32.71	$32.70	$32.70
Purchase #6	$238.72	6.560%	$254.38	$254.38	$254.40	$254.40
Purchase #7	$233.87	11.773%	$261.4035	$261.40	$261.40	$261.40
7 purchase totals =	$1,019.84		$1,123.6297	$1,123.62	$1,123.60	$1,123.70