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	$12.83	10.663%	$14.1981	$14.20	$14.20	$14.20
Purchase #2	$211.70	5.743%	$223.8579	$223.86	$223.85	$223.90
Purchase #3	$71.78	9.819%	$78.8281	$78.83	$78.85	$78.80
Purchase #4	$44.87	11.828%	$50.1772	$50.18	$50.20	$50.20
Purchase #5	$167.34	5.144%	$175.948	$175.95	$175.95	$175.90
Purchase #6	$133.71	11.736%	$149.4022	$149.40	$149.40	$149.40
Purchase #7	$38.53	3.775%	$39.9845	$39.98	$40.00	$40.00
7 purchase totals =	$680.76		$732.3960	$732.40	$732.45	$732.40