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	$71.31	5.831%	$75.4681	$75.47	$75.45	$75.50
Purchase #2	$153.71	13.827%	$174.9635	$174.96	$174.95	$175.00
Purchase #3	$152.40	4.703%	$159.5674	$159.57	$159.55	$159.60
Purchase #4	$220.46	10.491%	$243.5885	$243.59	$243.60	$243.60
Purchase #5	$51.96	6.285%	$55.2257	$55.23	$55.25	$55.20
Purchase #6	$37.85	12.865%	$42.7194	$42.72	$42.70	$42.70
Purchase #7	$133.83	9.750%	$146.8784	$146.88	$146.90	$146.90
7 purchase totals =	$821.52		$898.4110	$898.42	$898.40	$898.50