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	$100.85	10.295%	$111.2325	$111.23	$111.25	$111.20
Purchase #2	$104.95	7.613%	$112.9398	$112.94	$112.95	$112.90
Purchase #3	$246.96	9.133%	$269.5149	$269.51	$269.50	$269.50
Purchase #4	$229.29	11.204%	$254.9797	$254.98	$255.00	$255.00
Purchase #5	$57.52	12.256%	$64.5697	$64.57	$64.55	$64.60
Purchase #6	$184.44	12.799%	$208.0465	$208.05	$208.05	$208.00
Purchase #7	$97.58	5.790%	$103.2299	$103.23	$103.25	$103.20
7 purchase totals =	$1,021.59		$1,124.5130	$1,124.51	$1,124.55	$1,124.40