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	$194.98	10.602%	$215.6518	$215.65	$215.65	$215.70
Purchase #2	$206.28	6.840%	$220.3896	$220.39	$220.40	$220.40
Purchase #3	$57.29	6.693%	$61.1244	$61.12	$61.10	$61.10
Purchase #4	$158.63	6.291%	$168.6094	$168.61	$168.60	$168.60
Purchase #5	$26.59	5.590%	$28.0764	$28.08	$28.10	$28.10
Purchase #6	$124.48	11.752%	$139.1089	$139.11	$139.10	$139.10
Purchase #7	$137.74	5.466%	$145.2689	$145.27	$145.25	$145.30
7 purchase totals =	$905.99		$978.2294	$978.23	$978.20	$978.30