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	$55.32	8.249%	$59.8833	$59.88	$59.90	$59.90
Purchase #2	$80.88	12.337%	$90.8582	$90.86	$90.85	$90.90
Purchase #3	$69.99	13.871%	$79.6983	$79.70	$79.70	$79.70
Purchase #4	$44.37	9.383%	$48.5332	$48.53	$48.55	$48.50
Purchase #5	$163.66	9.637%	$179.4319	$179.43	$179.45	$179.40
Purchase #6	$62.34	9.545%	$68.2904	$68.29	$68.30	$68.30
Purchase #7	$168.44	10.173%	$185.5754	$185.58	$185.60	$185.60
7 purchase totals =	$645.00		$712.2707	$712.27	$712.35	$712.30