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	$85.90	11.308%	$95.6136	$95.61	$95.60	$95.60
Purchase #2	$83.30	8.576%	$90.4438	$90.44	$90.45	$90.40
Purchase #3	$19.48	13.757%	$22.1599	$22.16	$22.15	$22.20
Purchase #4	$162.34	10.866%	$179.9799	$179.98	$180.00	$180.00
Purchase #5	$103.76	13.547%	$117.8164	$117.82	$117.80	$117.80
Purchase #6	$169.96	13.121%	$192.2605	$192.26	$192.25	$192.30
Purchase #7	$47.95	7.153%	$51.3799	$51.38	$51.40	$51.40
7 purchase totals =	$672.69		$749.6540	$749.65	$749.65	$749.70