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	$243.75	10.283%	$268.8148	$268.81	$268.80	$268.80
Purchase #2	$227.40	4.424%	$237.4602	$237.46	$237.45	$237.50
Purchase #3	$188.49	10.856%	$208.9525	$208.95	$208.95	$209.00
Purchase #4	$165.68	13.862%	$188.6466	$188.65	$188.65	$188.60
Purchase #5	$20.72	3.587%	$21.4632	$21.46	$21.45	$21.50
Purchase #6	$81.83	10.748%	$90.6251	$90.63	$90.65	$90.60
Purchase #7	$87.56	5.525%	$92.3977	$92.40	$92.40	$92.40
7 purchase totals =	$1,015.43		$1,108.3601	$1,108.36	$1,108.35	$1,108.40