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	$213.78	13.599%	$242.8519	$242.85	$242.85	$242.90
Purchase #2	$97.37	11.702%	$108.7642	$108.76	$108.75	$108.80
Purchase #3	$217.86	4.863%	$228.4545	$228.45	$228.45	$228.50
Purchase #4	$62.47	4.714%	$65.4148	$65.41	$65.40	$65.40
Purchase #5	$190.53	6.772%	$203.4327	$203.43	$203.45	$203.40
Purchase #6	$116.58	9.345%	$127.4744	$127.47	$127.45	$127.50
Purchase #7	$77.93	4.454%	$81.401	$81.40	$81.40	$81.40
7 purchase totals =	$976.52		$1,057.7935	$1,057.77	$1,057.75	$1,057.90