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	$116.85	9.483%	$127.9309	$127.93	$127.95	$127.90
Purchase #2	$200.55	11.133%	$222.8772	$222.88	$222.90	$222.90
Purchase #3	$215.45	10.189%	$237.4022	$237.40	$237.40	$237.40
Purchase #4	$109.84	13.159%	$124.2938	$124.29	$124.30	$124.30
Purchase #5	$179.86	9.607%	$197.1392	$197.14	$197.15	$197.10
Purchase #6	$214.84	13.520%	$243.8864	$243.89	$243.90	$243.90
Purchase #7	$163.44	5.401%	$172.2674	$172.27	$172.25	$172.30
7 purchase totals =	$1,200.83		$1,325.7971	$1,325.80	$1,325.85	$1,325.80