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	$133.91	4.221%	$139.5623	$139.56	$139.55	$139.60
Purchase #2	$167.37	6.635%	$178.475	$178.48	$178.50	$178.50
Purchase #3	$114.73	4.458%	$119.8447	$119.84	$119.85	$119.80
Purchase #4	$116.81	12.758%	$131.7126	$131.71	$131.70	$131.70
Purchase #5	$233.62	9.454%	$255.7064	$255.71	$255.70	$255.70
Purchase #6	$118.50	7.414%	$127.2856	$127.29	$127.30	$127.30
Purchase #7	$197.83	7.331%	$212.3329	$212.33	$212.35	$212.30
7 purchase totals =	$1,082.77		$1,164.9195	$1,164.92	$1,164.95	$1,164.90