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	$241.41	10.439%	$266.6108	$266.61	$266.60	$266.60
Purchase #2	$171.25	10.614%	$189.4265	$189.43	$189.45	$189.40
Purchase #3	$73.97	5.620%	$78.1271	$78.13	$78.15	$78.10
Purchase #4	$182.46	3.513%	$188.8698	$188.87	$188.85	$188.90
Purchase #5	$247.47	3.269%	$255.5598	$255.56	$255.55	$255.60
Purchase #6	$92.76	6.437%	$98.731	$98.73	$98.75	$98.70
Purchase #7	$112.97	3.332%	$116.7342	$116.73	$116.75	$116.70
7 purchase totals =	$1,122.29		$1,194.0592	$1,194.06	$1,194.10	$1,194.00