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	$204.85	9.826%	$224.9786	$224.98	$225.00	$225.00
Purchase #2	$28.95	11.778%	$32.3597	$32.36	$32.35	$32.40
Purchase #3	$140.69	7.189%	$150.8042	$150.80	$150.80	$150.80
Purchase #4	$27.94	11.459%	$31.1416	$31.14	$31.15	$31.10
Purchase #5	$17.71	3.163%	$18.2702	$18.27	$18.25	$18.30
Purchase #6	$59.39	5.386%	$62.5887	$62.59	$62.60	$62.60
Purchase #7	$188.27	6.564%	$200.628	$200.63	$200.65	$200.60
7 purchase totals =	$667.80		$720.7710	$720.77	$720.80	$720.80