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	$187.67	4.606%	$196.3141	$196.31	$196.30	$196.30
Purchase #2	$109.49	3.181%	$112.9729	$112.97	$112.95	$113.00
Purchase #3	$86.28	7.577%	$92.8174	$92.82	$92.80	$92.80
Purchase #4	$200.66	12.366%	$225.4736	$225.47	$225.45	$225.50
Purchase #5	$118.55	8.693%	$128.8556	$128.86	$128.85	$128.90
Purchase #6	$144.85	11.757%	$161.88	$161.88	$161.90	$161.90
Purchase #7	$91.89	9.297%	$100.433	$100.43	$100.45	$100.40
7 purchase totals =	$939.39		$1,018.7466	$1,018.74	$1,018.70	$1,018.80