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	$97.68	9.392%	$106.8541	$106.85	$106.85	$106.90
Purchase #2	$52.45	10.405%	$57.9074	$57.91	$57.90	$57.90
Purchase #3	$139.68	3.636%	$144.7588	$144.76	$144.75	$144.80
Purchase #4	$52.46	3.538%	$54.316	$54.32	$54.30	$54.30
Purchase #5	$98.66	13.396%	$111.8765	$111.88	$111.90	$111.90
Purchase #6	$184.70	3.294%	$190.784	$190.78	$190.80	$190.80
Purchase #7	$141.97	4.149%	$147.8603	$147.86	$147.85	$147.90
7 purchase totals =	$767.60		$814.3571	$814.36	$814.35	$814.50