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	$193.86	6.249%	$205.9743	$205.97	$205.95	$206.00
Purchase #2	$119.72	9.757%	$131.4011	$131.40	$131.40	$131.40
Purchase #3	$148.46	3.433%	$153.5566	$153.56	$153.55	$153.60
Purchase #4	$62.85	6.259%	$66.7838	$66.78	$66.80	$66.80
Purchase #5	$125.55	11.796%	$140.3599	$140.36	$140.35	$140.40
Purchase #6	$79.74	3.404%	$82.4543	$82.45	$82.45	$82.50
Purchase #7	$249.96	3.547%	$258.8261	$258.83	$258.85	$258.80
7 purchase totals =	$980.14		$1,039.3561	$1,039.35	$1,039.35	$1,039.50