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	$45.40	13.401%	$51.4841	$51.48	$51.50	$51.50
Purchase #2	$122.41	6.617%	$130.5099	$130.51	$130.50	$130.50
Purchase #3	$159.85	3.497%	$165.44	$165.44	$165.45	$165.40
Purchase #4	$184.70	6.536%	$196.772	$196.77	$196.75	$196.80
Purchase #5	$23.44	8.322%	$25.3907	$25.39	$25.40	$25.40
Purchase #6	$181.52	9.504%	$198.7717	$198.77	$198.75	$198.80
Purchase #7	$174.72	9.642%	$191.5665	$191.57	$191.55	$191.60
7 purchase totals =	$892.04		$959.9349	$959.93	$959.90	$960.00