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	$247.44	6.141%	$262.6353	$262.64	$262.65	$262.60
Purchase #2	$107.27	9.424%	$117.3791	$117.38	$117.40	$117.40
Purchase #3	$138.55	6.824%	$148.0047	$148.00	$148.00	$148.00
Purchase #4	$67.30	7.389%	$72.2728	$72.27	$72.25	$72.30
Purchase #5	$160.81	7.189%	$172.3706	$172.37	$172.35	$172.40
Purchase #6	$161.63	4.251%	$168.5009	$168.50	$168.50	$168.50
Purchase #7	$164.53	10.808%	$182.3124	$182.31	$182.30	$182.30
7 purchase totals =	$1,047.53		$1,123.4758	$1,123.47	$1,123.45	$1,123.50