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	$107.46	4.751%	$112.5654	$112.57	$112.55	$112.60
Purchase #2	$103.65	12.753%	$116.8685	$116.87	$116.85	$116.90
Purchase #3	$160.89	8.124%	$173.9607	$173.96	$173.95	$174.00
Purchase #4	$35.38	4.596%	$37.0061	$37.01	$37.00	$37.00
Purchase #5	$71.52	12.710%	$80.6102	$80.61	$80.60	$80.60
Purchase #6	$220.95	10.680%	$244.5475	$244.55	$244.55	$244.50
Purchase #7	$51.43	10.345%	$56.7504	$56.75	$56.75	$56.80
7 purchase totals =	$751.28		$822.3088	$822.32	$822.25	$822.40