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	$125.64	3.746%	$130.3465	$130.35	$130.35	$130.30
Purchase #2	$112.51	13.386%	$127.5706	$127.57	$127.55	$127.60
Purchase #3	$55.61	12.446%	$62.5312	$62.53	$62.55	$62.50
Purchase #4	$35.25	9.141%	$38.4722	$38.47	$38.45	$38.50
Purchase #5	$149.31	3.366%	$154.3358	$154.34	$154.35	$154.30
Purchase #6	$16.96	7.851%	$18.2915	$18.29	$18.30	$18.30
Purchase #7	$46.28	11.370%	$51.542	$51.54	$51.55	$51.50
7 purchase totals =	$541.56		$583.0898	$583.09	$583.10	$583.00