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	$32.75	9.228%	$35.7722	$35.77	$35.75	$35.80
Purchase #2	$76.86	4.702%	$80.474	$80.47	$80.45	$80.50
Purchase #3	$130.59	10.523%	$144.332	$144.33	$144.35	$144.30
Purchase #4	$120.98	8.459%	$131.2137	$131.21	$131.20	$131.20
Purchase #5	$51.75	10.629%	$57.2505	$57.25	$57.25	$57.30
Purchase #6	$50.32	8.225%	$54.4588	$54.46	$54.45	$54.50
Purchase #7	$230.85	9.786%	$253.441	$253.44	$253.45	$253.40
7 purchase totals =	$694.10		$756.9422	$756.93	$756.90	$757.00