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	$40.45	4.496%	$42.2686	$42.27	$42.25	$42.30
Purchase #2	$75.95	8.859%	$82.6784	$82.68	$82.70	$82.70
Purchase #3	$12.77	13.783%	$14.5301	$14.53	$14.55	$14.50
Purchase #4	$72.98	6.461%	$77.6952	$77.70	$77.70	$77.70
Purchase #5	$103.46	10.810%	$114.644	$114.64	$114.65	$114.60
Purchase #6	$88.89	9.547%	$97.3763	$97.38	$97.40	$97.40
Purchase #7	$63.64	6.324%	$67.6646	$67.66	$67.65	$67.70
7 purchase totals =	$458.14		$496.8572	$496.86	$496.90	$496.90