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	$186.47	5.410%	$196.558	$196.56	$196.55	$196.60
Purchase #2	$145.65	12.478%	$163.8242	$163.82	$163.80	$163.80
Purchase #3	$97.73	4.596%	$102.2217	$102.22	$102.20	$102.20
Purchase #4	$237.90	6.873%	$254.2509	$254.25	$254.25	$254.30
Purchase #5	$37.32	9.472%	$40.855	$40.86	$40.85	$40.90
Purchase #6	$25.86	6.527%	$27.5479	$27.55	$27.55	$27.50
Purchase #7	$88.59	13.554%	$100.5975	$100.60	$100.60	$100.60
7 purchase totals =	$819.52		$885.8552	$885.86	$885.80	$885.90