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	$119.35	10.222%	$131.55	$131.55	$131.55	$131.60
Purchase #2	$250.57	11.182%	$278.5887	$278.59	$278.60	$278.60
Purchase #3	$66.87	5.325%	$70.4308	$70.43	$70.45	$70.40
Purchase #4	$144.83	13.806%	$164.8252	$164.83	$164.85	$164.80
Purchase #5	$189.47	11.664%	$211.5698	$211.57	$211.55	$211.60
Purchase #6	$165.97	3.102%	$171.1184	$171.12	$171.10	$171.10
Purchase #7	$46.83	5.581%	$49.4436	$49.44	$49.45	$49.40
7 purchase totals =	$983.89		$1,077.5265	$1,077.53	$1,077.55	$1,077.50