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	$55.60	12.386%	$62.4866	$62.49	$62.50	$62.50
Purchase #2	$10.25	3.831%	$10.6427	$10.64	$10.65	$10.60
Purchase #3	$127.66	10.859%	$141.5226	$141.52	$141.50	$141.50
Purchase #4	$168.34	6.707%	$179.6306	$179.63	$179.65	$179.60
Purchase #5	$198.99	13.773%	$226.3969	$226.40	$226.40	$226.40
Purchase #6	$173.43	6.590%	$184.859	$184.86	$184.85	$184.90
Purchase #7	$78.27	7.112%	$83.8366	$83.84	$83.85	$83.80
7 purchase totals =	$812.54		$889.3750	$889.38	$889.40	$889.30