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	$49.45	10.265%	$54.526	$54.53	$54.55	$54.50
Purchase #2	$10.98	4.199%	$11.4411	$11.44	$11.45	$11.40
Purchase #3	$235.84	5.257%	$248.2381	$248.24	$248.25	$248.20
Purchase #4	$129.89	9.536%	$142.2763	$142.28	$142.30	$142.30
Purchase #5	$100.89	4.645%	$105.5763	$105.58	$105.60	$105.60
Purchase #6	$127.90	11.689%	$142.8502	$142.85	$142.85	$142.90
Purchase #7	$154.43	8.748%	$167.9395	$167.94	$167.95	$167.90
7 purchase totals =	$809.38		$872.8475	$872.86	$872.95	$872.80