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	$212.53	5.441%	$224.0938	$224.09	$224.10	$224.10
Purchase #2	$249.48	8.202%	$269.9423	$269.94	$269.95	$269.90
Purchase #3	$112.75	9.130%	$123.0441	$123.04	$123.05	$123.00
Purchase #4	$38.40	5.554%	$40.5327	$40.53	$40.55	$40.50
Purchase #5	$203.47	8.772%	$221.3184	$221.32	$221.30	$221.30
Purchase #6	$95.46	10.533%	$105.5148	$105.51	$105.50	$105.50
Purchase #7	$43.73	6.196%	$46.4395	$46.44	$46.45	$46.40
7 purchase totals =	$955.82		$1,030.8856	$1,030.87	$1,030.90	$1,030.70