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	$68.61	5.612%	$72.4604	$72.46	$72.45	$72.50
Purchase #2	$101.96	10.352%	$112.5149	$112.51	$112.50	$112.50
Purchase #3	$80.95	9.569%	$88.6961	$88.70	$88.70	$88.70
Purchase #4	$59.54	8.128%	$64.3794	$64.38	$64.40	$64.40
Purchase #5	$169.39	4.441%	$176.9126	$176.91	$176.90	$176.90
Purchase #6	$224.72	4.434%	$234.6841	$234.68	$234.70	$234.70
Purchase #7	$75.31	3.332%	$77.8193	$77.82	$77.80	$77.80
7 purchase totals =	$780.48		$827.4668	$827.46	$827.45	$827.50