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	$164.57	12.500%	$185.1413	$185.14	$185.15	$185.10
Purchase #2	$139.99	3.496%	$144.8841	$144.88	$144.90	$144.90
Purchase #3	$40.50	8.442%	$43.919	$43.92	$43.90	$43.90
Purchase #4	$17.95	12.487%	$20.1914	$20.19	$20.20	$20.20
Purchase #5	$102.46	9.334%	$112.0236	$112.02	$112.00	$112.00
Purchase #6	$221.36	6.279%	$235.2592	$235.26	$235.25	$235.30
Purchase #7	$159.35	8.235%	$172.4725	$172.47	$172.45	$172.50
7 purchase totals =	$846.18		$913.8911	$913.88	$913.85	$913.90