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	$137.77	11.515%	$153.6342	$153.63	$153.65	$153.60
Purchase #2	$203.40	6.384%	$216.3851	$216.39	$216.40	$216.40
Purchase #3	$13.40	4.345%	$13.9822	$13.98	$14.00	$14.00
Purchase #4	$25.70	12.542%	$28.9233	$28.92	$28.90	$28.90
Purchase #5	$65.63	10.540%	$72.5474	$72.55	$72.55	$72.50
Purchase #6	$13.93	10.239%	$15.3563	$15.36	$15.35	$15.40
Purchase #7	$169.26	6.871%	$180.8899	$180.89	$180.90	$180.90
7 purchase totals =	$629.09		$681.7184	$681.72	$681.75	$681.70