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	$196.25	5.404%	$206.8554	$206.86	$206.85	$206.90
Purchase #2	$158.33	7.483%	$170.1778	$170.18	$170.20	$170.20
Purchase #3	$106.90	4.196%	$111.3855	$111.39	$111.40	$111.40
Purchase #4	$39.70	10.557%	$43.8911	$43.89	$43.90	$43.90
Purchase #5	$150.34	12.269%	$168.7852	$168.79	$168.80	$168.80
Purchase #6	$212.95	10.720%	$235.7782	$235.78	$235.80	$235.80
Purchase #7	$51.68	11.677%	$57.7147	$57.71	$57.70	$57.70
7 purchase totals =	$916.15		$994.5879	$994.60	$994.65	$994.70