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	$245.82	13.305%	$278.5264	$278.53	$278.55	$278.50
Purchase #2	$105.26	7.783%	$113.4524	$113.45	$113.45	$113.50
Purchase #3	$190.93	4.698%	$199.8999	$199.90	$199.90	$199.90
Purchase #4	$51.52	4.625%	$53.9028	$53.90	$53.90	$53.90
Purchase #5	$226.95	13.853%	$258.3894	$258.39	$258.40	$258.40
Purchase #6	$154.95	9.620%	$169.8562	$169.86	$169.85	$169.90
Purchase #7	$101.90	6.864%	$108.8944	$108.89	$108.90	$108.90
7 purchase totals =	$1,077.33		$1,182.9215	$1,182.92	$1,182.95	$1,183.00