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	$216.37	9.317%	$236.5292	$236.53	$236.55	$236.50
Purchase #2	$49.58	4.174%	$51.6495	$51.65	$51.65	$51.60
Purchase #3	$144.69	12.152%	$162.2727	$162.27	$162.25	$162.30
Purchase #4	$93.54	5.812%	$98.9765	$98.98	$99.00	$99.00
Purchase #5	$150.95	4.738%	$158.102	$158.10	$158.10	$158.10
Purchase #6	$65.56	7.429%	$70.4305	$70.43	$70.45	$70.40
Purchase #7	$28.54	13.495%	$32.3915	$32.39	$32.40	$32.40
7 purchase totals =	$749.23		$810.3519	$810.35	$810.40	$810.30