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	$160.70	7.193%	$172.2592	$172.26	$172.25	$172.30
Purchase #2	$178.61	4.541%	$186.7207	$186.72	$186.70	$186.70
Purchase #3	$162.33	7.513%	$174.5259	$174.53	$174.55	$174.50
Purchase #4	$66.64	9.650%	$73.0708	$73.07	$73.05	$73.10
Purchase #5	$54.31	12.506%	$61.102	$61.10	$61.10	$61.10
Purchase #6	$229.65	4.680%	$240.3976	$240.40	$240.40	$240.40
Purchase #7	$148.67	5.336%	$156.603	$156.60	$156.60	$156.60
7 purchase totals =	$1,000.91		$1,064.6792	$1,064.68	$1,064.65	$1,064.70