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	$143.54	10.449%	$158.5385	$158.54	$158.55	$158.50
Purchase #2	$117.95	7.783%	$127.13	$127.13	$127.15	$127.10
Purchase #3	$208.67	3.139%	$215.2202	$215.22	$215.20	$215.20
Purchase #4	$93.72	13.219%	$106.1088	$106.11	$106.10	$106.10
Purchase #5	$121.80	4.304%	$127.0423	$127.04	$127.05	$127.00
Purchase #6	$173.79	12.401%	$195.3417	$195.34	$195.35	$195.30
Purchase #7	$19.81	8.296%	$21.4534	$21.45	$21.45	$21.50
7 purchase totals =	$879.28		$950.8349	$950.83	$950.85	$950.70