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	$98.53	11.351%	$109.7141	$109.71	$109.70	$109.70
Purchase #2	$42.94	13.874%	$48.8975	$48.90	$48.90	$48.90
Purchase #3	$168.55	9.609%	$184.746	$184.75	$184.75	$184.70
Purchase #4	$175.58	12.560%	$197.6328	$197.63	$197.65	$197.60
Purchase #5	$244.72	4.797%	$256.4592	$256.46	$256.45	$256.50
Purchase #6	$36.60	10.725%	$40.5254	$40.53	$40.55	$40.50
Purchase #7	$93.74	10.328%	$103.4215	$103.42	$103.40	$103.40
7 purchase totals =	$860.66		$941.3965	$941.40	$941.40	$941.30