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	$168.80	9.351%	$184.5845	$184.58	$184.60	$184.60
Purchase #2	$182.58	4.540%	$190.8691	$190.87	$190.85	$190.90
Purchase #3	$51.98	7.497%	$55.8769	$55.88	$55.90	$55.90
Purchase #4	$54.65	8.803%	$59.4608	$59.46	$59.45	$59.50
Purchase #5	$156.66	9.360%	$171.3234	$171.32	$171.30	$171.30
Purchase #6	$227.27	3.559%	$235.3585	$235.36	$235.35	$235.40
Purchase #7	$213.91	13.116%	$241.9664	$241.97	$241.95	$242.00
7 purchase totals =	$1,055.85		$1,139.4396	$1,139.44	$1,139.40	$1,139.60