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	$93.94	7.128%	$100.636	$100.64	$100.65	$100.60
Purchase #2	$75.45	8.874%	$82.1454	$82.15	$82.15	$82.10
Purchase #3	$58.47	6.860%	$62.481	$62.48	$62.50	$62.50
Purchase #4	$116.85	8.587%	$126.8839	$126.88	$126.90	$126.90
Purchase #5	$100.42	8.486%	$108.9416	$108.94	$108.95	$108.90
Purchase #6	$79.93	8.132%	$86.4299	$86.43	$86.45	$86.40
Purchase #7	$98.62	10.448%	$108.9238	$108.92	$108.90	$108.90
7 purchase totals =	$623.68		$676.4416	$676.44	$676.50	$676.30