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	$188.65	11.273%	$209.9165	$209.92	$209.90	$209.90
Purchase #2	$146.82	7.812%	$158.2896	$158.29	$158.30	$158.30
Purchase #3	$156.31	11.734%	$174.6514	$174.65	$174.65	$174.70
Purchase #4	$97.39	12.395%	$109.4615	$109.46	$109.45	$109.50
Purchase #5	$58.28	12.285%	$65.4397	$65.44	$65.45	$65.40
Purchase #6	$13.80	5.786%	$14.5985	$14.60	$14.60	$14.60
Purchase #7	$61.94	3.343%	$64.0107	$64.01	$64.00	$64.00
7 purchase totals =	$723.19		$796.3679	$796.37	$796.35	$796.40