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	$168.72	11.786%	$188.6053	$188.61	$188.60	$188.60
Purchase #2	$66.87	5.518%	$70.5599	$70.56	$70.55	$70.60
Purchase #3	$69.59	3.628%	$72.1147	$72.11	$72.10	$72.10
Purchase #4	$134.74	11.516%	$150.2567	$150.26	$150.25	$150.30
Purchase #5	$62.77	5.406%	$66.1633	$66.16	$66.15	$66.20
Purchase #6	$109.30	11.348%	$121.7034	$121.70	$121.70	$121.70
Purchase #7	$194.32	9.856%	$213.4722	$213.47	$213.45	$213.50
7 purchase totals =	$806.31		$882.8755	$882.87	$882.80	$883.00