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	$143.34	6.660%	$152.8864	$152.89	$152.90	$152.90
Purchase #2	$32.90	10.844%	$36.4677	$36.47	$36.45	$36.50
Purchase #3	$70.47	10.357%	$77.7686	$77.77	$77.75	$77.80
Purchase #4	$121.30	4.445%	$126.6918	$126.69	$126.70	$126.70
Purchase #5	$115.46	7.248%	$123.8285	$123.83	$123.85	$123.80
Purchase #6	$241.99	12.172%	$271.445	$271.45	$271.45	$271.40
Purchase #7	$71.40	4.147%	$74.361	$74.36	$74.35	$74.40
7 purchase totals =	$796.86		$863.4490	$863.46	$863.45	$863.50