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	$176.25	4.141%	$183.5485	$183.55	$183.55	$183.50
Purchase #2	$141.49	11.870%	$158.2849	$158.28	$158.30	$158.30
Purchase #3	$198.36	9.680%	$217.5612	$217.56	$217.55	$217.60
Purchase #4	$75.37	13.815%	$85.7824	$85.78	$85.80	$85.80
Purchase #5	$36.26	6.121%	$38.4795	$38.48	$38.50	$38.50
Purchase #6	$128.28	12.131%	$143.8416	$143.84	$143.85	$143.80
Purchase #7	$249.77	9.224%	$272.8088	$272.81	$272.80	$272.80
7 purchase totals =	$1,005.78		$1,100.3069	$1,100.30	$1,100.35	$1,100.30