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	$199.26	13.173%	$225.5085	$225.51	$225.50	$225.50
Purchase #2	$234.77	7.328%	$251.9739	$251.97	$251.95	$252.00
Purchase #3	$98.83	5.325%	$104.0927	$104.09	$104.10	$104.10
Purchase #4	$87.83	3.445%	$90.8557	$90.86	$90.85	$90.90
Purchase #5	$53.52	9.442%	$58.5734	$58.57	$58.55	$58.60
Purchase #6	$106.78	9.498%	$116.922	$116.92	$116.90	$116.90
Purchase #7	$245.43	13.494%	$278.5483	$278.55	$278.55	$278.50
7 purchase totals =	$1,026.42		$1,126.4745	$1,126.47	$1,126.40	$1,126.50