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	$39.73	12.203%	$44.5783	$44.58	$44.60	$44.60
Purchase #2	$139.33	9.300%	$152.2877	$152.29	$152.30	$152.30
Purchase #3	$239.97	11.221%	$266.897	$266.90	$266.90	$266.90
Purchase #4	$86.63	3.116%	$89.3294	$89.33	$89.35	$89.30
Purchase #5	$249.62	4.855%	$261.7391	$261.74	$261.75	$261.70
Purchase #6	$107.68	5.293%	$113.3795	$113.38	$113.40	$113.40
Purchase #7	$146.51	4.749%	$153.4678	$153.47	$153.45	$153.50
7 purchase totals =	$1,009.47		$1,081.6788	$1,081.69	$1,081.75	$1,081.70