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	$164.58	12.725%	$185.5228	$185.52	$185.50	$185.50
Purchase #2	$20.26	3.539%	$20.977	$20.98	$21.00	$21.00
Purchase #3	$99.89	13.679%	$113.554	$113.55	$113.55	$113.60
Purchase #4	$127.41	11.462%	$142.0137	$142.01	$142.00	$142.00
Purchase #5	$13.43	4.629%	$14.0517	$14.05	$14.05	$14.10
Purchase #6	$158.34	3.570%	$163.9927	$163.99	$164.00	$164.00
Purchase #7	$179.59	3.864%	$186.5294	$186.53	$186.55	$186.50
7 purchase totals =	$763.50		$826.6413	$826.63	$826.65	$826.70