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	$168.88	10.628%	$186.8286	$186.83	$186.85	$186.80
Purchase #2	$241.89	13.864%	$275.4256	$275.43	$275.45	$275.40
Purchase #3	$38.54	3.784%	$39.9984	$40.00	$40.00	$40.00
Purchase #4	$182.54	3.524%	$188.9727	$188.97	$188.95	$189.00
Purchase #5	$133.60	11.868%	$149.4556	$149.46	$149.45	$149.50
Purchase #6	$250.55	7.281%	$268.7925	$268.79	$268.80	$268.80
Purchase #7	$139.79	4.422%	$145.9715	$145.97	$145.95	$146.00
7 purchase totals =	$1,155.79		$1,255.4449	$1,255.45	$1,255.45	$1,255.50