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	$164.67	13.110%	$186.2582	$186.26	$186.25	$186.30
Purchase #2	$36.38	6.200%	$38.6356	$38.64	$38.65	$38.60
Purchase #3	$10.45	9.582%	$11.4513	$11.45	$11.45	$11.50
Purchase #4	$40.45	11.619%	$45.1499	$45.15	$45.15	$45.10
Purchase #5	$73.96	3.731%	$76.7194	$76.72	$76.70	$76.70
Purchase #6	$43.62	5.223%	$45.8983	$45.90	$45.90	$45.90
Purchase #7	$14.76	11.832%	$16.5064	$16.51	$16.50	$16.50
7 purchase totals =	$384.29		$420.6191	$420.63	$420.60	$420.60