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	$150.41	10.543%	$166.2677	$166.27	$166.25	$166.30
Purchase #2	$65.57	10.728%	$72.6043	$72.60	$72.60	$72.60
Purchase #3	$127.57	3.256%	$131.7237	$131.72	$131.70	$131.70
Purchase #4	$225.51	8.762%	$245.2692	$245.27	$245.25	$245.30
Purchase #5	$238.54	10.249%	$262.988	$262.99	$263.00	$263.00
Purchase #6	$76.52	6.270%	$81.3178	$81.32	$81.30	$81.30
Purchase #7	$220.81	7.710%	$237.8345	$237.83	$237.85	$237.80
7 purchase totals =	$1,104.93		$1,198.0052	$1,198.00	$1,197.95	$1,198.00