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	$48.79	11.773%	$54.534	$54.53	$54.55	$54.50
Purchase #2	$80.64	7.169%	$86.4211	$86.42	$86.40	$86.40
Purchase #3	$5.32	3.206%	$5.4906	$5.49	$5.50	$5.50
Purchase #4	$213.53	4.402%	$222.9296	$222.93	$222.95	$222.90
Purchase #5	$66.31	9.512%	$72.6174	$72.62	$72.60	$72.60
Purchase #6	$23.56	8.663%	$25.601	$25.60	$25.60	$25.60
Purchase #7	$14.81	4.603%	$15.4917	$15.49	$15.50	$15.50
7 purchase totals =	$452.96		$483.0854	$483.08	$483.10	$483.00