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	$247.82	13.847%	$282.1356	$282.14	$282.15	$282.10
Purchase #2	$80.29	12.309%	$90.1729	$90.17	$90.15	$90.20
Purchase #3	$56.79	3.787%	$58.9406	$58.94	$58.95	$58.90
Purchase #4	$54.71	13.726%	$62.2195	$62.22	$62.20	$62.20
Purchase #5	$68.88	5.301%	$72.5313	$72.53	$72.55	$72.50
Purchase #6	$224.43	4.471%	$234.4643	$234.46	$234.45	$234.50
Purchase #7	$27.87	11.246%	$31.0043	$31.00	$31.00	$31.00
7 purchase totals =	$760.79		$831.4685	$831.46	$831.45	$831.40