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	$51.91	8.667%	$56.409	$56.41	$56.40	$56.40
Purchase #2	$38.73	8.723%	$42.1084	$42.11	$42.10	$42.10
Purchase #3	$196.29	4.673%	$205.4626	$205.46	$205.45	$205.50
Purchase #4	$167.63	6.791%	$179.0138	$179.01	$179.00	$179.00
Purchase #5	$208.89	9.451%	$228.6322	$228.63	$228.65	$228.60
Purchase #6	$116.93	13.229%	$132.3987	$132.40	$132.40	$132.40
Purchase #7	$172.87	8.438%	$187.4568	$187.46	$187.45	$187.50
7 purchase totals =	$953.25		$1,031.4815	$1,031.48	$1,031.45	$1,031.50