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	$66.86	9.833%	$73.4343	$73.43	$73.45	$73.40
Purchase #2	$190.89	4.581%	$199.6347	$199.63	$199.65	$199.60
Purchase #3	$24.61	12.157%	$27.6018	$27.60	$27.60	$27.60
Purchase #4	$231.48	7.737%	$249.3896	$249.39	$249.40	$249.40
Purchase #5	$123.78	10.657%	$136.9712	$136.97	$136.95	$137.00
Purchase #6	$230.70	4.693%	$241.5268	$241.53	$241.55	$241.50
Purchase #7	$153.68	11.708%	$171.6729	$171.67	$171.65	$171.70
7 purchase totals =	$1,022.00		$1,100.2313	$1,100.22	$1,100.25	$1,100.20