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	$119.28	7.187%	$127.8527	$127.85	$127.85	$127.90
Purchase #2	$126.55	3.600%	$131.1058	$131.11	$131.10	$131.10
Purchase #3	$111.81	8.860%	$121.7164	$121.72	$121.70	$121.70
Purchase #4	$189.66	4.550%	$198.2895	$198.29	$198.30	$198.30
Purchase #5	$134.82	3.173%	$139.0978	$139.10	$139.10	$139.10
Purchase #6	$114.45	3.243%	$118.1616	$118.16	$118.15	$118.20
Purchase #7	$66.72	5.488%	$70.3816	$70.38	$70.40	$70.40
7 purchase totals =	$863.29		$906.6054	$906.61	$906.60	$906.70