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	$38.78	12.484%	$43.6213	$43.62	$43.60	$43.60
Purchase #2	$118.33	6.217%	$125.6866	$125.69	$125.70	$125.70
Purchase #3	$173.65	13.333%	$196.8028	$196.80	$196.80	$196.80
Purchase #4	$115.65	3.851%	$120.1037	$120.10	$120.10	$120.10
Purchase #5	$113.88	11.537%	$127.0183	$127.02	$127.00	$127.00
Purchase #6	$23.54	3.709%	$24.4131	$24.41	$24.40	$24.40
Purchase #7	$125.29	11.285%	$139.429	$139.43	$139.45	$139.40
7 purchase totals =	$709.12		$777.0748	$777.07	$777.05	$777.00