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	$48.75	10.533%	$53.8848	$53.88	$53.90	$53.90
Purchase #2	$39.27	12.265%	$44.0865	$44.09	$44.10	$44.10
Purchase #3	$162.55	7.739%	$175.1297	$175.13	$175.15	$175.10
Purchase #4	$66.40	9.434%	$72.6642	$72.66	$72.65	$72.70
Purchase #5	$14.58	6.630%	$15.5467	$15.55	$15.55	$15.50
Purchase #6	$11.33	6.265%	$12.0398	$12.04	$12.05	$12.00
Purchase #7	$74.72	13.778%	$85.0149	$85.01	$85.00	$85.00
7 purchase totals =	$417.60		$458.3666	$458.36	$458.40	$458.30