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	$239.65	5.793%	$253.5329	$253.53	$253.55	$253.50
Purchase #2	$80.48	13.547%	$91.3826	$91.38	$91.40	$91.40
Purchase #3	$102.55	9.449%	$112.2399	$112.24	$112.25	$112.20
Purchase #4	$40.64	8.488%	$44.0895	$44.09	$44.10	$44.10
Purchase #5	$31.29	4.120%	$32.5791	$32.58	$32.60	$32.60
Purchase #6	$115.73	10.183%	$127.5148	$127.51	$127.50	$127.50
Purchase #7	$90.53	12.150%	$101.5294	$101.53	$101.55	$101.50
7 purchase totals =	$700.87		$762.8682	$762.86	$762.95	$762.80