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	$177.60	3.787%	$184.3257	$184.33	$184.35	$184.30
Purchase #2	$86.29	5.142%	$90.727	$90.73	$90.75	$90.70
Purchase #3	$54.71	4.307%	$57.0664	$57.07	$57.05	$57.10
Purchase #4	$71.38	9.125%	$77.8934	$77.89	$77.90	$77.90
Purchase #5	$52.61	13.681%	$59.8076	$59.81	$59.80	$59.80
Purchase #6	$230.88	4.241%	$240.6716	$240.67	$240.65	$240.70
Purchase #7	$22.64	11.706%	$25.2902	$25.29	$25.30	$25.30
7 purchase totals =	$696.11		$735.7819	$735.79	$735.80	$735.80