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	$161.86	6.508%	$172.3938	$172.39	$172.40	$172.40
Purchase #2	$73.41	6.488%	$78.1728	$78.17	$78.15	$78.20
Purchase #3	$97.32	3.662%	$100.8839	$100.88	$100.90	$100.90
Purchase #4	$85.56	7.540%	$92.0112	$92.01	$92.00	$92.00
Purchase #5	$87.86	12.774%	$99.0832	$99.08	$99.10	$99.10
Purchase #6	$78.93	8.786%	$85.8648	$85.86	$85.85	$85.90
Purchase #7	$146.34	6.406%	$155.7145	$155.71	$155.70	$155.70
7 purchase totals =	$731.28		$784.1242	$784.10	$784.10	$784.20