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	$203.61	8.138%	$220.1798	$220.18	$220.20	$220.20
Purchase #2	$233.86	11.648%	$261.1	$261.10	$261.10	$261.10
Purchase #3	$175.36	13.195%	$198.4988	$198.50	$198.50	$198.50
Purchase #4	$59.69	3.710%	$61.9045	$61.90	$61.90	$61.90
Purchase #5	$90.92	3.826%	$94.3986	$94.40	$94.40	$94.40
Purchase #6	$122.82	3.369%	$126.9578	$126.96	$126.95	$127.00
Purchase #7	$106.59	5.584%	$112.542	$112.54	$112.55	$112.50
7 purchase totals =	$992.85		$1,075.5815	$1,075.58	$1,075.60	$1,075.60