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	$55.51	12.604%	$62.5065	$62.51	$62.50	$62.50
Purchase #2	$83.73	10.514%	$92.5334	$92.53	$92.55	$92.50
Purchase #3	$153.25	13.631%	$174.1395	$174.14	$174.15	$174.10
Purchase #4	$29.76	13.447%	$33.7618	$33.76	$33.75	$33.80
Purchase #5	$51.71	3.163%	$53.3456	$53.35	$53.35	$53.30
Purchase #6	$241.66	7.365%	$259.4583	$259.46	$259.45	$259.50
Purchase #7	$206.92	3.496%	$214.1539	$214.15	$214.15	$214.20
7 purchase totals =	$822.54		$889.8990	$889.90	$889.90	$889.90