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	$60.71	4.114%	$63.2076	$63.21	$63.20	$63.20
Purchase #2	$98.68	10.336%	$108.8796	$108.88	$108.90	$108.90
Purchase #3	$42.63	11.573%	$47.5636	$47.56	$47.55	$47.60
Purchase #4	$132.31	5.393%	$139.4455	$139.45	$139.45	$139.40
Purchase #5	$30.31	7.298%	$32.522	$32.52	$32.50	$32.50
Purchase #6	$30.97	5.779%	$32.7598	$32.76	$32.75	$32.80
Purchase #7	$152.93	7.737%	$164.7622	$164.76	$164.75	$164.80
7 purchase totals =	$548.54		$589.1403	$589.14	$589.10	$589.20