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	$186.55	5.503%	$196.8158	$196.82	$196.80	$196.80
Purchase #2	$226.94	11.831%	$253.7893	$253.79	$253.80	$253.80
Purchase #3	$183.88	13.327%	$208.3857	$208.39	$208.40	$208.40
Purchase #4	$137.97	3.229%	$142.4251	$142.43	$142.45	$142.40
Purchase #5	$204.92	5.652%	$216.5021	$216.50	$216.50	$216.50
Purchase #6	$34.25	7.489%	$36.815	$36.82	$36.80	$36.80
Purchase #7	$51.56	9.272%	$56.3406	$56.34	$56.35	$56.30
7 purchase totals =	$1,026.07		$1,111.0736	$1,111.09	$1,111.10	$1,111.00