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	$51.93	9.523%	$56.8753	$56.88	$56.90	$56.90
Purchase #2	$55.58	7.155%	$59.5567	$59.56	$59.55	$59.60
Purchase #3	$167.29	5.238%	$176.0527	$176.05	$176.05	$176.10
Purchase #4	$248.27	3.139%	$256.0632	$256.06	$256.05	$256.10
Purchase #5	$151.32	11.688%	$169.0063	$169.01	$169.00	$169.00
Purchase #6	$195.49	10.523%	$216.0614	$216.06	$216.05	$216.10
Purchase #7	$122.39	4.661%	$128.0946	$128.09	$128.10	$128.10
7 purchase totals =	$992.27		$1,061.7102	$1,061.71	$1,061.70	$1,061.90