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	$14.82	4.109%	$15.429	$15.43	$15.45	$15.40
Purchase #2	$109.71	12.124%	$123.0112	$123.01	$123.00	$123.00
Purchase #3	$57.44	4.393%	$59.9633	$59.96	$59.95	$60.00
Purchase #4	$7.39	8.753%	$8.0368	$8.04	$8.05	$8.00
Purchase #5	$25.46	9.699%	$27.9294	$27.93	$27.95	$27.90
Purchase #6	$170.51	6.788%	$182.0842	$182.08	$182.10	$182.10
Purchase #7	$48.42	9.728%	$53.1303	$53.13	$53.15	$53.10
7 purchase totals =	$433.75		$469.5842	$469.58	$469.65	$469.50