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	$69.59	9.358%	$76.1022	$76.10	$76.10	$76.10
Purchase #2	$50.32	5.605%	$53.1404	$53.14	$53.15	$53.10
Purchase #3	$54.34	9.105%	$59.2877	$59.29	$59.30	$59.30
Purchase #4	$224.74	3.869%	$233.4352	$233.44	$233.45	$233.40
Purchase #5	$128.61	9.256%	$140.5141	$140.51	$140.50	$140.50
Purchase #6	$174.53	12.451%	$196.2607	$196.26	$196.25	$196.30
Purchase #7	$54.32	5.869%	$57.508	$57.51	$57.50	$57.50
7 purchase totals =	$756.45		$816.2483	$816.25	$816.25	$816.20