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	$44.38	9.783%	$48.7217	$48.72	$48.70	$48.70
Purchase #2	$78.40	9.632%	$85.9515	$85.95	$85.95	$86.00
Purchase #3	$145.61	3.616%	$150.8753	$150.88	$150.90	$150.90
Purchase #4	$126.96	10.667%	$140.5028	$140.50	$140.50	$140.50
Purchase #5	$63.37	6.668%	$67.5955	$67.60	$67.60	$67.60
Purchase #6	$54.55	11.617%	$60.8871	$60.89	$60.90	$60.90
Purchase #7	$29.35	3.594%	$30.4048	$30.40	$30.40	$30.40
7 purchase totals =	$542.62		$584.9387	$584.94	$584.95	$585.00