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	$203.65	12.677%	$229.4667	$229.47	$229.45	$229.50
Purchase #2	$81.27	10.218%	$89.5742	$89.57	$89.55	$89.60
Purchase #3	$234.46	8.378%	$254.1031	$254.10	$254.10	$254.10
Purchase #4	$177.39	7.553%	$190.7883	$190.79	$190.80	$190.80
Purchase #5	$147.54	11.721%	$164.8332	$164.83	$164.85	$164.80
Purchase #6	$224.30	10.848%	$248.6321	$248.63	$248.65	$248.60
Purchase #7	$233.94	10.655%	$258.8663	$258.87	$258.85	$258.90
7 purchase totals =	$1,302.55		$1,436.2639	$1,436.26	$1,436.25	$1,436.30