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	$158.47	3.574%	$164.1337	$164.13	$164.15	$164.10
Purchase #2	$193.37	11.757%	$216.1045	$216.10	$216.10	$216.10
Purchase #3	$123.59	6.481%	$131.5999	$131.60	$131.60	$131.60
Purchase #4	$32.64	4.238%	$34.0233	$34.02	$34.00	$34.00
Purchase #5	$122.29	7.353%	$131.282	$131.28	$131.30	$131.30
Purchase #6	$80.46	5.134%	$84.5908	$84.59	$84.60	$84.60
Purchase #7	$237.51	10.560%	$262.5911	$262.59	$262.60	$262.60
7 purchase totals =	$948.33		$1,024.3253	$1,024.31	$1,024.35	$1,024.30