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	$124.50	13.504%	$141.3125	$141.31	$141.30	$141.30
Purchase #2	$141.76	11.339%	$157.8342	$157.83	$157.85	$157.80
Purchase #3	$113.99	9.206%	$124.4839	$124.48	$124.50	$124.50
Purchase #4	$98.42	10.478%	$108.7324	$108.73	$108.75	$108.70
Purchase #5	$174.71	12.350%	$196.2867	$196.29	$196.30	$196.30
Purchase #6	$169.45	12.559%	$190.7312	$190.73	$190.75	$190.70
Purchase #7	$191.35	4.565%	$200.0851	$200.09	$200.10	$200.10
7 purchase totals =	$1,014.18		$1,119.4660	$1,119.46	$1,119.55	$1,119.40