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	$13.47	7.288%	$14.4517	$14.45	$14.45	$14.50
Purchase #2	$176.49	3.383%	$182.4607	$182.46	$182.45	$182.50
Purchase #3	$101.66	7.153%	$108.9317	$108.93	$108.95	$108.90
Purchase #4	$18.98	11.746%	$21.2094	$21.21	$21.20	$21.20
Purchase #5	$152.44	9.194%	$166.4553	$166.46	$166.45	$166.50
Purchase #6	$104.74	13.275%	$118.6442	$118.64	$118.65	$118.60
Purchase #7	$95.96	5.140%	$100.8923	$100.89	$100.90	$100.90
7 purchase totals =	$663.74		$713.0453	$713.04	$713.05	$713.10