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	$210.89	12.152%	$236.5174	$236.52	$236.50	$236.50
Purchase #2	$108.40	10.778%	$120.0834	$120.08	$120.10	$120.10
Purchase #3	$24.65	13.371%	$27.946	$27.95	$27.95	$27.90
Purchase #4	$173.75	8.863%	$189.1495	$189.15	$189.15	$189.10
Purchase #5	$132.48	5.640%	$139.9519	$139.95	$139.95	$140.00
Purchase #6	$78.63	8.817%	$85.5628	$85.56	$85.55	$85.60
Purchase #7	$158.90	12.844%	$179.3091	$179.31	$179.30	$179.30
7 purchase totals =	$887.70		$978.5201	$978.52	$978.50	$978.50