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	$113.77	13.258%	$128.8536	$128.85	$128.85	$128.90
Purchase #2	$162.51	9.231%	$177.5113	$177.51	$177.50	$177.50
Purchase #3	$195.93	6.833%	$209.3179	$209.32	$209.30	$209.30
Purchase #4	$100.90	6.854%	$107.8157	$107.82	$107.80	$107.80
Purchase #5	$172.83	5.725%	$182.7245	$182.72	$182.70	$182.70
Purchase #6	$214.85	10.710%	$237.8604	$237.86	$237.85	$237.90
Purchase #7	$83.77	7.535%	$90.0821	$90.08	$90.10	$90.10
7 purchase totals =	$1,044.56		$1,134.1655	$1,134.16	$1,134.10	$1,134.20