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	$207.59	5.271%	$218.5321	$218.53	$218.55	$218.50
Purchase #2	$74.97	4.337%	$78.2214	$78.22	$78.20	$78.20
Purchase #3	$175.33	12.447%	$197.1533	$197.15	$197.15	$197.20
Purchase #4	$78.83	13.371%	$89.3704	$89.37	$89.35	$89.40
Purchase #5	$229.75	4.443%	$239.9578	$239.96	$239.95	$240.00
Purchase #6	$221.36	3.354%	$228.7844	$228.78	$228.80	$228.80
Purchase #7	$13.97	3.127%	$14.4068	$14.41	$14.40	$14.40
7 purchase totals =	$1,001.80		$1,066.4262	$1,066.42	$1,066.40	$1,066.50