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	$153.45	7.402%	$164.8084	$164.81	$164.80	$164.80
Purchase #2	$78.67	10.732%	$87.1129	$87.11	$87.10	$87.10
Purchase #3	$157.26	5.303%	$165.5995	$165.60	$165.60	$165.60
Purchase #4	$225.81	13.275%	$255.7863	$255.79	$255.80	$255.80
Purchase #5	$186.78	11.864%	$208.9396	$208.94	$208.95	$208.90
Purchase #6	$105.86	3.663%	$109.7377	$109.74	$109.75	$109.70
Purchase #7	$116.33	9.215%	$127.0498	$127.05	$127.05	$127.00
7 purchase totals =	$1,024.16		$1,119.0342	$1,119.04	$1,119.05	$1,118.90