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	$165.67	10.422%	$182.9361	$182.94	$182.95	$182.90
Purchase #2	$158.47	3.340%	$163.7629	$163.76	$163.75	$163.80
Purchase #3	$81.66	9.550%	$89.4585	$89.46	$89.45	$89.50
Purchase #4	$11.51	9.208%	$12.5698	$12.57	$12.55	$12.60
Purchase #5	$101.98	3.265%	$105.3096	$105.31	$105.30	$105.30
Purchase #6	$116.61	12.569%	$131.2667	$131.27	$131.25	$131.30
Purchase #7	$178.54	7.728%	$192.3376	$192.34	$192.35	$192.30
7 purchase totals =	$814.44		$877.6412	$877.65	$877.60	$877.70