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	$239.69	6.125%	$254.371	$254.37	$254.35	$254.40
Purchase #2	$131.33	6.485%	$139.8468	$139.85	$139.85	$139.80
Purchase #3	$233.39	10.525%	$257.9543	$257.95	$257.95	$258.00
Purchase #4	$55.36	12.774%	$62.4317	$62.43	$62.45	$62.40
Purchase #5	$130.29	5.147%	$136.996	$137.00	$137.00	$137.00
Purchase #6	$70.28	12.368%	$78.9722	$78.97	$78.95	$79.00
Purchase #7	$140.95	10.746%	$156.0965	$156.10	$156.10	$156.10
7 purchase totals =	$1,001.29		$1,086.6685	$1,086.67	$1,086.65	$1,086.70