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	$63.46	7.105%	$67.9688	$67.97	$67.95	$68.00
Purchase #2	$98.65	6.397%	$104.9606	$104.96	$104.95	$105.00
Purchase #3	$230.78	4.592%	$241.3774	$241.38	$241.40	$241.40
Purchase #4	$82.53	5.767%	$87.2895	$87.29	$87.30	$87.30
Purchase #5	$113.31	12.301%	$127.2483	$127.25	$127.25	$127.20
Purchase #6	$238.29	3.354%	$246.2822	$246.28	$246.30	$246.30
Purchase #7	$96.75	6.559%	$103.0958	$103.10	$103.10	$103.10
7 purchase totals =	$923.77		$978.2226	$978.23	$978.25	$978.30