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	$160.90	8.784%	$175.0335	$175.03	$175.05	$175.00
Purchase #2	$216.43	10.164%	$238.4279	$238.43	$238.45	$238.40
Purchase #3	$112.40	7.128%	$120.4119	$120.41	$120.40	$120.40
Purchase #4	$130.59	13.388%	$148.0734	$148.07	$148.05	$148.10
Purchase #5	$212.27	12.397%	$238.5851	$238.59	$238.60	$238.60
Purchase #6	$169.58	12.221%	$190.3044	$190.30	$190.30	$190.30
Purchase #7	$164.31	7.713%	$176.9832	$176.98	$177.00	$177.00
7 purchase totals =	$1,166.48		$1,287.8194	$1,287.81	$1,287.85	$1,287.80