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	$238.81	11.570%	$266.4403	$266.44	$266.45	$266.40
Purchase #2	$190.54	12.255%	$213.8907	$213.89	$213.90	$213.90
Purchase #3	$104.62	6.285%	$111.1954	$111.20	$111.20	$111.20
Purchase #4	$99.72	12.839%	$112.5231	$112.52	$112.50	$112.50
Purchase #5	$204.54	4.604%	$213.957	$213.96	$213.95	$214.00
Purchase #6	$98.45	12.290%	$110.5495	$110.55	$110.55	$110.50
Purchase #7	$125.95	9.158%	$137.4845	$137.48	$137.50	$137.50
7 purchase totals =	$1,062.63		$1,166.0405	$1,166.04	$1,166.05	$1,166.00