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	$217.78	7.468%	$234.0438	$234.04	$234.05	$234.00
Purchase #2	$128.43	6.187%	$136.376	$136.38	$136.40	$136.40
Purchase #3	$19.88	7.238%	$21.3189	$21.32	$21.30	$21.30
Purchase #4	$143.62	11.508%	$160.1478	$160.15	$160.15	$160.10
Purchase #5	$127.37	9.439%	$139.3925	$139.39	$139.40	$139.40
Purchase #6	$45.38	10.236%	$50.0251	$50.03	$50.05	$50.00
Purchase #7	$17.80	9.597%	$19.5083	$19.51	$19.50	$19.50
7 purchase totals =	$700.26		$760.8124	$760.82	$760.85	$760.70