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	$178.90	9.747%	$196.3374	$196.34	$196.35	$196.30
Purchase #2	$113.81	12.696%	$128.2593	$128.26	$128.25	$128.30
Purchase #3	$198.82	12.355%	$223.3842	$223.38	$223.40	$223.40
Purchase #4	$248.48	13.438%	$281.8707	$281.87	$281.85	$281.90
Purchase #5	$92.81	8.696%	$100.8808	$100.88	$100.90	$100.90
Purchase #6	$34.96	4.510%	$36.5367	$36.54	$36.55	$36.50
Purchase #7	$186.65	7.563%	$200.7663	$200.77	$200.75	$200.80
7 purchase totals =	$1,054.43		$1,168.0354	$1,168.04	$1,168.05	$1,168.10