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	$241.59	8.205%	$261.4125	$261.41	$261.40	$261.40
Purchase #2	$154.63	4.194%	$161.1152	$161.12	$161.10	$161.10
Purchase #3	$148.78	5.257%	$156.6014	$156.60	$156.60	$156.60
Purchase #4	$203.52	10.828%	$225.5571	$225.56	$225.55	$225.60
Purchase #5	$65.74	9.184%	$71.7776	$71.78	$71.80	$71.80
Purchase #6	$185.47	13.747%	$210.9666	$210.97	$210.95	$211.00
Purchase #7	$54.45	12.754%	$61.3946	$61.39	$61.40	$61.40
7 purchase totals =	$1,054.18		$1,148.8250	$1,148.83	$1,148.80	$1,148.90