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	$153.84	13.477%	$174.573	$174.57	$174.55	$174.60
Purchase #2	$29.75	9.438%	$32.5578	$32.56	$32.55	$32.60
Purchase #3	$182.34	9.314%	$199.3231	$199.32	$199.30	$199.30
Purchase #4	$127.43	3.267%	$131.5931	$131.59	$131.60	$131.60
Purchase #5	$15.76	12.451%	$17.7223	$17.72	$17.70	$17.70
Purchase #6	$43.69	13.424%	$49.5549	$49.55	$49.55	$49.60
Purchase #7	$91.76	13.778%	$104.4027	$104.40	$104.40	$104.40
7 purchase totals =	$644.57		$709.7269	$709.71	$709.65	$709.80