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	$112.81	6.612%	$120.269	$120.27	$120.25	$120.30
Purchase #2	$89.43	12.140%	$100.2868	$100.29	$100.30	$100.30
Purchase #3	$189.97	12.585%	$213.8777	$213.88	$213.90	$213.90
Purchase #4	$68.27	13.501%	$77.4871	$77.49	$77.50	$77.50
Purchase #5	$144.38	11.464%	$160.9317	$160.93	$160.95	$160.90
Purchase #6	$238.59	4.579%	$249.515	$249.52	$249.50	$249.50
Purchase #7	$120.72	3.105%	$124.4684	$124.47	$124.45	$124.50
7 purchase totals =	$964.17		$1,046.8357	$1,046.85	$1,046.85	$1,046.90