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	$86.93	10.497%	$96.055	$96.06	$96.05	$96.10
Purchase #2	$163.27	5.704%	$172.5829	$172.58	$172.60	$172.60
Purchase #3	$5.89	7.240%	$6.3164	$6.32	$6.30	$6.30
Purchase #4	$95.59	8.545%	$103.7582	$103.76	$103.75	$103.80
Purchase #5	$158.50	4.358%	$165.4074	$165.41	$165.40	$165.40
Purchase #6	$110.94	12.495%	$124.802	$124.80	$124.80	$124.80
Purchase #7	$250.93	9.553%	$274.9013	$274.90	$274.90	$274.90
7 purchase totals =	$872.05		$943.8232	$943.83	$943.80	$943.90