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	$50.30	10.859%	$55.7621	$55.76	$55.75	$55.80
Purchase #2	$162.82	10.853%	$180.4909	$180.49	$180.50	$180.50
Purchase #3	$136.65	4.517%	$142.8225	$142.82	$142.80	$142.80
Purchase #4	$221.57	9.183%	$241.9168	$241.92	$241.90	$241.90
Purchase #5	$231.63	7.874%	$249.8685	$249.87	$249.85	$249.90
Purchase #6	$217.40	10.106%	$239.3704	$239.37	$239.35	$239.40
Purchase #7	$39.27	8.515%	$42.6138	$42.61	$42.60	$42.60
7 purchase totals =	$1,059.64		$1,152.8450	$1,152.84	$1,152.75	$1,152.90