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	$169.93	6.440%	$180.8735	$180.87	$180.85	$180.90
Purchase #2	$143.83	9.331%	$157.2508	$157.25	$157.25	$157.30
Purchase #3	$181.59	9.252%	$198.3907	$198.39	$198.40	$198.40
Purchase #4	$116.97	5.535%	$123.4443	$123.44	$123.45	$123.40
Purchase #5	$7.35	3.551%	$7.611	$7.61	$7.60	$7.60
Purchase #6	$151.95	13.471%	$172.4192	$172.42	$172.40	$172.40
Purchase #7	$53.73	12.236%	$60.3044	$60.30	$60.30	$60.30
7 purchase totals =	$825.35		$900.2939	$900.28	$900.25	$900.30