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	$94.36	8.395%	$102.2815	$102.28	$102.30	$102.30
Purchase #2	$182.28	7.312%	$195.6083	$195.61	$195.60	$195.60
Purchase #3	$29.64	8.639%	$32.2006	$32.20	$32.20	$32.20
Purchase #4	$150.82	5.115%	$158.5344	$158.53	$158.55	$158.50
Purchase #5	$131.97	4.221%	$137.5405	$137.54	$137.55	$137.50
Purchase #6	$106.47	4.863%	$111.6476	$111.65	$111.65	$111.60
Purchase #7	$197.76	12.528%	$222.5354	$222.54	$222.55	$222.50
7 purchase totals =	$893.30		$960.3483	$960.35	$960.40	$960.20