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	$40.45	9.144%	$44.1487	$44.15	$44.15	$44.10
Purchase #2	$100.92	11.677%	$112.7044	$112.70	$112.70	$112.70
Purchase #3	$158.60	12.238%	$178.0095	$178.01	$178.00	$178.00
Purchase #4	$196.25	5.788%	$207.609	$207.61	$207.60	$207.60
Purchase #5	$95.59	5.357%	$100.7108	$100.71	$100.70	$100.70
Purchase #6	$6.66	9.181%	$7.2715	$7.27	$7.25	$7.30
Purchase #7	$77.33	12.374%	$86.8988	$86.90	$86.90	$86.90
7 purchase totals =	$675.80		$737.3527	$737.35	$737.30	$737.30