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	$211.25	9.299%	$230.8941	$230.89	$230.90	$230.90
Purchase #2	$247.46	6.287%	$263.0178	$263.02	$263.00	$263.00
Purchase #3	$151.99	12.372%	$170.7942	$170.79	$170.80	$170.80
Purchase #4	$81.75	5.792%	$86.485	$86.49	$86.50	$86.50
Purchase #5	$90.61	5.610%	$95.6932	$95.69	$95.70	$95.70
Purchase #6	$228.81	9.517%	$250.5858	$250.59	$250.60	$250.60
Purchase #7	$127.45	12.155%	$142.9415	$142.94	$142.95	$142.90
7 purchase totals =	$1,139.32		$1,240.4116	$1,240.41	$1,240.45	$1,240.40