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	$208.64	6.655%	$222.525	$222.53	$222.55	$222.50
Purchase #2	$98.26	4.127%	$102.3152	$102.32	$102.30	$102.30
Purchase #3	$145.38	13.114%	$164.4451	$164.45	$164.45	$164.40
Purchase #4	$172.71	10.820%	$191.3972	$191.40	$191.40	$191.40
Purchase #5	$101.42	3.857%	$105.3318	$105.33	$105.35	$105.30
Purchase #6	$76.67	7.809%	$82.6572	$82.66	$82.65	$82.70
Purchase #7	$82.81	13.234%	$93.7691	$93.77	$93.75	$93.80
7 purchase totals =	$885.89		$962.4406	$962.46	$962.45	$962.40