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	$110.88	3.235%	$114.467	$114.47	$114.45	$114.50
Purchase #2	$216.33	8.485%	$234.6856	$234.69	$234.70	$234.70
Purchase #3	$86.51	4.556%	$90.4514	$90.45	$90.45	$90.50
Purchase #4	$206.56	4.130%	$215.0909	$215.09	$215.10	$215.10
Purchase #5	$155.27	11.535%	$173.1804	$173.18	$173.20	$173.20
Purchase #6	$29.83	11.389%	$33.2273	$33.23	$33.25	$33.20
Purchase #7	$43.90	9.579%	$48.1052	$48.11	$48.10	$48.10
7 purchase totals =	$849.28		$909.2078	$909.22	$909.25	$909.30