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	$107.31	11.605%	$119.7633	$119.76	$119.75	$119.80
Purchase #2	$95.40	4.527%	$99.7188	$99.72	$99.70	$99.70
Purchase #3	$77.94	4.543%	$81.4808	$81.48	$81.50	$81.50
Purchase #4	$86.69	11.527%	$96.6828	$96.68	$96.70	$96.70
Purchase #5	$151.68	4.462%	$158.448	$158.45	$158.45	$158.40
Purchase #6	$210.69	12.579%	$237.1927	$237.19	$237.20	$237.20
Purchase #7	$95.51	4.594%	$99.8977	$99.90	$99.90	$99.90
7 purchase totals =	$825.22		$893.1841	$893.18	$893.20	$893.20